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UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 903 

Contribution from the Bureau of Entomology 
L. O. HOWARD, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



April 22, 1921 



THE 
GRAPE PHYLLOXERA IN CALIFORNIA 



By 

W. M. DAVIDSON, Scientific Assistant, and 

R. L. NOUGARET, Entomological Assistant, 

Deciduous Fruit Insect Investigations 



CONTENTS 



Page 

California History 1 

Accidental and Natural Spread .... 7 

Distribution of Phylloxera in California . 11 

Vineyard Destruction 15 

Nomenclature and Synonymy of the 

Grape Phylloxera 26 

Biology of the Grape Phylloxera in Cali- 
fornia 27 

The Radicicole 44 



Page 

The Nymph and Winged Form .... 73 

Nymphicals or Intermediate Forms . . 82 

The Sexual Forms 90 

The Gallicole and its Relation to Cali- 
fornia Conditions 95 

Effects of Water and Heat on Phylloxera 98 

Diffusion of Phylloxera 100 

Summary 122 

Literature Cited 127 




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UNITED STATES DEPARTMENT OF AGRICULTURE 




BULLETIN No. 903 

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Contribution from the Bureau of Entomology 
L. O. HOWARD, Chief 




4 Sw7"^r*s<t» 



Washington, D.C. 



PROFESSIONAL PAPER 



April 22, 1921 



THE GRAPE PHYLLOXERA 1 IN CALIFORNIA, 

By W. M. Davidson, Scientific Assistant, and R. L. Nougaret, 2 Entomological 
Assistant, Deciduous Fruit Insect Investigations. 

CONTENTS. 



Page. 

California history 1 

Accidental and natural spread 7 

Distribution of phylloxera in Cali- 
fornia 11 

Vineyard destruction 15 

Nomenclature and synonymy of the 

grape phylloxera 26 

Biology of the grape phylloxera in 

California 27 

The radicicole 44 



Page. 

The nymph and winged form 73 

Nymphicals or intermediate forms 82 

The sexual forms 90 

The gallicole and its relation to Cali- 
fornia conditions 95 

Effects of water and heat on phyl- 
loxera 98 

Diffusion of phylloxera 100 

Summary 122 

Literature cited 127 



CALIFORNIA HISTORY. _ 

EARLY VINE PLANTING IN CALIFORNIA. 



It has long 



The grape phylloxera is not native to California, 
been recognized as originating in North America, but its native 
habitat is east of the Rocky Mountains. The insect has not established 
itself upon the native vine of California (Vitis calif ornica) in the 
wild state, whereas in Arizona it is established on native vines. 

1 Phylloxera vitifoliae (Fitch). 

2 Now in charge, Viticulture Service, California Department of Agriculture, Sacramento, 
Calif. 

Note. — In connection with other work in California, the office of Deciduous Fruit 
Insect Investigations, Bureau of Entomology, in cooperation with the Bureau of riant 
Industry, has been engaged in an investigation of the grape phylloxera during several 
years past, with principal headquarters for the work at Walnut Creek. The work 
inaugurated by E. L. Jenne, upon his death was taken over by S. W. Foster, assisted by 
R. L. Nougaret. Upon Mr. Foster's leaving the service, the investigation was continued 
by Messrs. Nougaret and Davidson, the latter giving especial attention to biological and 
life-history studies and the former to investigations in the field and to remedial opera- 
tions. The present report deals with the history, injuries, and life history of the insect 
in California. Remedial measures will be made the subject of another publication. It 
has been necessary to omit an extended bibliography of the subject. — A. L. Quaintance, 
Entomologist in Charge of Deciduous Fruit Insect Investigations. 
1900° — 21 1 



2 BULLETIN C03, U. S. DEPARTMENT OF AGRICULTURE. 

More specifically, the insect is a native of the Mississippi Valley, 
where the vines have developed a resistance to phylloxera, and such 
species as Vitis riparia, V. rupestris, V. aestivalis, etc., thrive, not- 
withstanding the presence of the insect. These wild species possess 
varying degrees of immunity and through scientific selection and 
hybridization have yielded types of vines possessing inherent de- 
grees of immunity, known to viticulture as resistant vines, or re- 
sistant stocks when designated as a root upon which to graft com- 
mercial varieties of grapes in order to circumvent the ravages of 
phylloxera. 

Vitis calif ornica is a wild species of vine found not only in Cali- 
fornia but throughout the Pacific coast. Because normally found free 
of phylloxera in its wild state, it was at one time tried out as a 
resistant stock upon which to graft commercial varieties, but proved 
a complete failure in all but one or two instances. Even under normal 
conditions and environment, when once attacked it succumbs to the 
injury by the insect. 3 

The Mission grape is a cultivated variety of Vitis vinifera, and 
although of European origin, its introduction to the Pacific coast is 
so intimately related with the first settlement of California under 
Spanish rule that it well deserves the oft- attributed title of " Cali- 
fornia grape" (7) 4 . The Mission grape was introduced into Cali- 
fornia by the Padres of the Roman Catholic missions. As early as 
1524 (18, p. 17), while Cortez was governor of Mexico, then called 
New Spain, seeds and plants were most often part of the cargo 
of vessels plying between the mother country and her colonies. 
Grapes and olives are plants mentioned as being among these. It is 
to be assumed that about that time Vitis vinifera varieties were intro- 
duced into Mexico from Spain 5 through both cuttings and seeds 
(1, v. 2, p. 131-133; v. 3, p. 613). 

3 In the Annual Report of the California Board of State Viticultural Commissioners 
for 1887, published in 1888, pages 47-48, may be found the following : " While visiting 
Mr. Hagan's vineyard, we were led to examine an old vine — V. calif ornica— which 
appeared like one infested with phylloxera. This surmise proved correct * *. 

" The commission has often sought for evidences of phylloxera on our wild vines in 
their native state, but up to this time none has been found, this being the first case of 
the kind discovered." (See "Literature cited (5)," p. 127.) 

4 Numbers in parentheses refer to ." Literature cited," p. 11*7. 

5 In this connection F. T. Bioletti, professor of viticulture at the University of Cali- 
fornia, writes as follows: "No one has yet been able to trace the Mission grape with 
certainty to any European variety. It is a remarkable coincidence, if nothing else, that 
a Sardinian grape known as the Monica resembles the Mission very closely. The Monica 
is said to be a favorite grape of the monks in Sardinia, and it seems probable that the 
missionary monks of Mexico, finding it difficult to transport cuttings from their original 
homos, obtained seeds of the grape which they liked the best and that from the seedlings 
grown they ehose the one wbich most resembled the grape they were looking for. If this 
is in accordance with the facts, the Mission is simply a seedling of the Monica." 

He further advances the suggestion that the Mission might he a seedling of the Monica, 
as published in a report (2) of the viticultural work of the agricultural experiment 
station of the University of California * * * 1887-1893. 



THE GRAPE PHYLLOXERA 1ST CALIFORNIA. 3 

Later, in the early part of the eighteenth century, a long line of 
missions was established throughout the peninsula of Lower Cali- 
fornia, the Mission of Loreto being the first, in 1697. These missions 
all grew grapes. The vines were furnished to them originally by 
the colonies of Mexico. As missions were founded, products and 
plants were furnished to the new one by the older established ones, 
and grapes are almost always mentioned as being cultivated by the 
Padres. 

The Mission of San Diego was the first to be founded in upper 
California, and the vines planted there were brought from the mis- 
sions of Lower California. As no other variety but the Mission 
grape is known to have been cultivated by the different missions 
which were founded in after years, it is to be presumed that it was 
introduced into this State with the founding of the Mission of San 
Diego, 1769. 

The Mission is a long-lived, vigorous, and thrifty vine, as is 
attested by two remarkable specimens. The one planted in 1775, and 
still living, is on the property of the San Gabriel Mission in Los 
Angeles County, is trained on an arbor, covers 9,000 square feet, and 
its trunk just below the surface of the soil has a circumference of 
9 feet. The other, planted in 1842 near Carpenteria, died in 1915, 
presumably of the "Anaheim disease." It measured at its base 8J 
feet in circumference; at a height of 6J feet it divided into three 
branches, one of which measured 3J feet in circumference. As an 
arbor it covered one- fourth acre, and in 1895 yielded its maximum 
crop of 10 tons, its average crop being estimated at 5 tons. 6 

The Mission grape in early days was planted by the Padres around 
the missions and was used both as a table grape and especially for 
making wine. Gen. Vallejo (7) is authority for the statement that 
the Mission grapes grown at the Sonoma Mission were of a better 
quality than those grown at the other missions in California, and 
that a recognized superior quality of wine was made from them.. 

It was probably because of this reputation that the first commercial 
vineyards of wine grapes were established in the vicinity of the town 
of Sonoma. In this district the grape phylloxera was first discov- 
ered, and the dying of the vines, which for some time had puzzled the 
viticulturists, was finally determined to be the result of this insect's 
attack. An importation of vines from Europe of unparallelled im- 
portance up to that time for California, and one which may ade- 
quately be termed a "pioneer importation," occurred at about this 
time and very shortly prior to the discovery in France of the 
phylloxera, thereby furnishing grounds for the subsequent report, 
more or less widely spread throughout the State and which persists 

6 Details of its history can be obtained from the secretary of the Carpenteria Chamber 
of Commerce. 



4 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

even at this late date, though refuted at different times by investi- 
gators, that this importation of European vines was responsible for 
the introduction of phylloxera into California. This is a mistaken 
idea. The history of the grape industry virtually proves that the 
insect was imported with American species or varieties of grapes 
from east of the Rocky Mountains. 

FIRST DISCOVERY OF GRAPE PHYLLOXERA IN CALIFORNIA. 

The first evidence of phylloxera infestation in California dates as 
far back as 1858. The dissemination of phylloxera continued for 
years in California before the existence of the pest was known, al- 
though its destructive work was observed, commented on, and desig- 
nated a disease of vines from unknown causes. Eeference to the 
first discovery and determination of the insect in California is to be 
found in a report (4, p. 108-111) dated August 28, 1880, and sub- 
mitted by H. Appleton. In his report the first ravages witnessed in 
California are discussed, and from them is inferred the date of in- 
troduction of the insect. Extracts from this report follow : 

On the nineteenth of August, 1873, an insect was found on the roots of 
grapevines by H. Appleton and O. W. Craig, in the vineyard of the latter, 
situated two miles north from Sonoma Town, on the west side of Sonoma 
Creek. An investigation was ordered at the time, for though the insect was 
identified as " the insect, or louse, known in Europe by the title of phylloxera- 
vastatrix, and in the United States as pemphygus vitifoliae," there existed a 
doubt in the minds of the investigators, because the injury was confined wholly 
to the roots of the vine, and no symptoms of injury such as recorded in 
Europe and in Eastern North America could be detected on the leaves. 

Prom information received from Mr. A. F. Haraszthy and Captain E. Cutter, 
Superintendent of the Buena Vista Company's vineyards, I am able to give 
the following facts in regard to their large vineyards : 

A vineyard of about one thousand vines was planted in 1834-35, and was 
watered every year. In 1850 and 1852 the vineyard was largely increased, and 
the system of irrigation was stopped. In 1857 about two hundred thousand 
vines were set out, and in 1858 one hundred acres were put in vines (six 
hundred and eighty vines to the acre). Again, in 1860, fifty acres were 
laid out. In 1862, Colonel A. Haraszthy planted 70,000 European vines, and 
it was among these vines the disease increased most rapidly. 

In the Spring of 1863 the Buena Vista Company was incorporated, and in 
the Spring of 1864 that company planted 100,000 vines. 

As early as 1860 decayed and dying vines were noticed in the vineyard, and 
they were taken up and others planted in their places. An examination was 
made to discover the cause of the disease in these vines, and it was attributed 
to alkali water, which was found a few feet underground. The roots were de- 
cayed. No examination by microscope of these roots was made. Vines 
died from time to time, showing short growth, small and colorless grapes, 
early yellow leaves — in fact, all the symptoms were ot served of vines dying 
from the vine pest. 

In 1868 about 3 acres of diseased vines were taken up (planted in 1850) 
on the north side of the dwelling bouse, and new vines planted, which grew 
well, showing little signs of decay till they were lour years old, at which 
time (1873) the Phylloxera Committee, of the Viticultural Club, found the 
phylloxera on several vines. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 5 

The facts of this statement are significant and by no means am- 
biguous if considered in the light of the knowledge possessed to-day 
of the life history and habits of phylloxera, the nature of its in- 
jury, and the progress of its ravages. 

This report also indicates how and when the first impulse was 
given to the development of the grape and wine industries of the 
State, then in their infancy. As interest grew in this direction, 
better varieties of grapes than the Mission would naturally be sought 
and given a trial. This was the case with the eastern variety of 
grape, the Catawba, a vine susceptible to the attack of phylloxera 
because of its fleshy roots and successfully grown at that time in 
the East as a wine grape. A weekly agricultural paper, the Cali- 
fornia Farmer (6), under date of Thursday, January 23, 1855, in an 
editorial article entitled " The Catawba Grape," says : 

We sincerely esteem the Catawba grape, one of the very best varieties for 
cultivation in California. Longworth of Ohio, whose famous Catawba Cham- 
pagne is now esteemed equal to any wine imported, says it is the very finest 
wine grape known. Will be found far superior to our California Grape [Mis- 
sion]. We earnestly urge our cultivators to give the Catawba a careful trial. 

The same agricultural periodical from time to time that same year 
published other articles 7 eulogizing not only the Catawba but also 
other vines of eastern varieties and quoting fabulous yields in wine 
and profits. 

Articles such as these undoubtedly influenced the planting of east- 
ern varieties, if only as an experiment. Can it be doubted that many 
vines were brought from the East to California and the phylloxera 
introduced with them ? 

The variety of grape planted in 1850-1852 in the Buena Vista 
vineyard is not mentioned. It is more than likely that the major 
part of the planting was of Mission. If these vines were inoculated 
with phylloxera shortly afterwards by means of a few eastern grape- 
vines planted near by, the vineyard would have experienced a spread 
of invasion as related above by Appleton. Evidence of the insects' 
injury would be apparent as affecting only a few vines during a few 
years or up to about 1860, and eight years later the vines, covering 
an area of 3 acres, would have become so dwarfed and nonproduc- 
tive, with perhaps a few dead, that it would be necessary to grub 
them up. That this vineyard trouble was due to phylloxera is em- 
phasized by the further statement that the 3 acres were again 
replanted with new vines, and during the four following }^ears 
(1869-1872) the vines were again affected in a similar manner, but 
to a slighter degree, just as a recurrence of infestation would act if 
vines were planted in infested soil. Finally, in 1873, just five years 

7 E. g., " What are the best grapes ; " " Extracts of the Cincinnati Gazette." 



6 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

after the replanting of the 3 acres, the committee of the Viticultural 
Club discovered the phylloxera on the roots of several of the replants. 

The history of this vineyard proves conclusively by direct and cir- 
cumstantial evidence that the trouble was due to phylloxera. It 
localizes the infestation, describes the progress and spread of the 
injury, and, by fixing dates, determines the period of time the prog- 
ress covered. Finally, the presence of the insect is discovered and 
its identity determined. 

In 1861 Gov. Downey, of California, appointed three commis- 
sioners to work in the interests of the grape industry, two of the 
members of this commission being Don Juan Warner and A. Ha- 
raszthy. The latter was sent to Europe to purchase for the State 
for distribution different varieties of grapes, and the result was the 
importation of 200,000 cuttings and rooted vines, comprising 1,400 
different varieties of grapes from all the vine-growing countries of 
Europe and also from Asia Minor. It may be that some of these im- 
ported rooted vines harbored phylloxera, which already had caused 
considerable damage to vines in France, although the insect was only 
discovered in that country the following year (1862). It is quite 
likely that a good portion of the 70,000 vines planted out on the 
Buena Vista vineyard in 1862 and referred to in Appleton's report 
were propagated from this importation and that the pest may have 
been introduced simultaneously with the planting of the vines. The 
rapid destruction of the vineyard, as stated, however, could have been 
brought about in the case of the young vines just as well by infesta- 
tion communicated by the old vineyard. 

The history of the Orleans Hill vineyard furnishes an insight into 
the methods of establishing vineyards with varieties of grapes im- 
ported from Europe in the early days of grape culture in California, 
and helps to give grounds for the belief that the earliest and original 
introduction of phylloxera into this State was due to eastern varieties 
of grapes only. 

Data of this history are contained in a report, dated 1880, submitted 
by the owner of the vineyard (4, p. 112). In 1853 the owner im- 
ported from Nassau, on the Rhine, in Germany, 15 varieties of grape 
cuttings (vinifera) and planted them in his garden near Slitters 
Fort, Sacramento, where they flourished splendidly and showed no 
signs of disease. In 1859-60 many vines were propagated here for 
planting the Orleans Hill vineyard in Cache Creek Canyon, Solano 
County. This vineyard was set out in two different situations, part 
being on a hillside and part in a flat. In the latter situation the 
soil was of a stiff clayey nature and the vines did not do as well as 
on the more friable hillside soil, and this necessitated replanting, for 
which there were procured later from Napa some Zinfandel vines. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 7 

The date when these replants were procured is not specified, but was 
probably about 1864 or 1865. Before the date of replanting the 
phylloxera had infested the S'onoma Creek district and had spread 
to Napa County. 

In 1859 a horticultural exhibit was held in the agricultural hall 
just completed that year at Sacramento, and the records of the State 
Agricultural Society mention exceptionally good exhibits of grapes 
by progressive fruit growers. The eastern grape Catawba is twice 
mentioned. 

From another report (4, p. 29-30) we learn to what extent the 
eastern varieties of grapes were grown prior to 1875 in El Dorado 
County. No mention is made of earlier dates, but it is more than 
probable that the European grapes were already supplanting the 
eastern ones, judging by the few of the latter type which were 
planted in later years and which to-day are found only in family 
vineyards and gardens. This report, written by Mr. Gr. G. Blan- 
chard, commissioner of the State board of viticulture, further stated 
that what was true of El Dorado County could also be said of 
Nevada, Placer, Amador, Calaveras, Tuolumne, and Mariposa Coun- 
ties. A passage reads : 

The proportions and kinds (grapes) growing, taking one hundred as the sum, 
are as follows : Mission, or native grapes, sixty-eight ; Catawba and Isabella, 
ten ; White Muscat, Muscatella, Malaga, six ; Tokay, Black Morocco, Malvoisies, 
one ; Zinfandel, Riesling, two. The other thirteen are made up of numerous 
other varieties, such as Sweet Water, Black July, Hartford Prolific, Cloantha, 
and Concord, and some others. 

In this enumeration eastern grapes would represent approximately 
23 per cent of the varieties grown. We thus see the important part 
played by eastern varieties of grapes in the earliest plantings and 
can conceive how the pest was introduced directly from its natural 
habitat. 

ACCIDENTAL AND NATURAL SPREAD. 

Centers of infestation, when compared according to the modes of 
dissemination which they engender, are of two kinds: Accidental 
and natural. An accidental distribution center would be a nursery 
which imported, unwittingly, phylloxera-infested grapes, propagated 
the vines, and by so doing bred the insect and disseminated it with 
the sale and shipment of these vines. The same is true when vines 
are procured from phylloxera-infested districts. For new plant- 
ings or replants, such a center would be the infested locality in Napa, 
from which the Zinfandel vines were the means of introducing the 
pest into a locality as yet free from it. In turn, the Orleans Hill 
vineyard became a natural distributing center because the insect 
by its natural increase and habit spread to other parts of the same 
vineyard or even to other vineyards of the district. 



8 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

Infestation from accidental distributing centers may be avoided 
by strictly enforced quarantine measures. 

Accidental spread has been the main cause of most of the phyllox- 
era infestation throughout the vineyards of California because of 
its being an initial inoculation, developing later into a center of 
natural dissemination. 

A general survey of the growth of the grape industry, which 
at times, as in the late eighties and early nineties, attained the 
proportion of a boom, furnishes an indication of the accidental 
spread which took place concurrently. 

Cuttings were used almost exclusively for planting vineyards in 
preference to rooted vines, the latter being used for replanting 
"misses," and even then not commonly used. As will be shown 
later, there is little, if any, danger in disseminating the phylloxera 
from cuttings, unless these are heeled in in infested soil while await- 
ing shipment. It is for this reason that the accidental diffusion 
was greatly restricted. If rooted vines had been commonly used, 
originating from the same district as the cuttings, the accidental 
diffusion would have been so general as perhaps to have precluded 
before long the growing of vinifera vines on their own roots. 

THE WINGED MIGRANT NOT A FACTOR IN SPREAD UNDER CALIFORNIA 

CONDITIONS. 

Profiting by the investigations and experiments that were being 
carried on in France, the University of California in conjunction 
with the State Board of Viticulture made extensive efforts to ar- 
rest the ravages of the phylloxera, and made investigations pertain- 
ing to its life history and habits. These deserve special mention 
in this report. 

Dr. F. W. Morse (16) of Oakland, Calif., during the period 
1881-1886, as an assistant in the General Agricultural Laboratory, 
discovered in the course of his investigations on August 26, 1884, 
specimens of the gall louse or leaf -inhabiting form of the phylloxera. 
As is noted under the heading " The gallicole and i^ts relation to 
California conditions" (p. 95), this is the only recorded instance 
of the finding in California of the leaf galls. In this connection it 
may be said that in the experimental vinej^ards of the Bureau of 
Plant Industry, United States Department of Agriculture, in which 
are collected many varieties and hybrids of species of American 
vines, not a few of which are susceptible to leaf galls when culti- 
vated in the Eastern or Middle States, an exceptionally good field 
for observation is offered. Mr. G. C. Husmann, under whose direc- 
tion these vineyards are conducted, states that the leaf gall, to his 
knowledge, has never been found in them. Extensive correspondence 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 9 

with entomologists and prominent viticulturists in California elicited 
the same information. 

Laboratory experiments, conducted under favorable conditions to 
obtain winter eggs with the existing strain of phylloxera in Cali- 
fornia, have failed to go beyond the production of the winged form 
in specially devised cages, although in other laboratory experiments 
the sexed forms were produced and the discovery in the natural state 
of a single winter egg must be mentioned. 

A study of the life history has corroborated the observations of 
Dr. Morse relating to the sterility of a portion of the winged migrants 
and to the sterility of some and the debility of the remainder of their 
progeny. The writers' observations demonstrate that the normal life 
cycle of the insect in California is wholly parthenogenetic and that 
the natural spread, or diffusion, is due entirely to young radicicole 
larvae possessing migratory instincts, at least during July, August, 
and September, and to which has been given the name of "wan- 
derers " to distinguish them from " migrants," a term which com- 
monly is applied to winged forms of the Aphididae. 

The conclusions of the investigations of Dr. Morse point to the 
possibility of such a condition, though not affirming that the winged 
migrant is not responsible for the diffusion of the species in Cali- 
fornia. The late Prof. E. W. Hilgard (14) shared this view, which 
he expounded in his report, in which he indicates the discovery by 
him of one of the first phylloxera spots in Napa Valley, as follows : 

The first phylloxerated " spot " within the Napa Valley was observed by me 
in 1877, close to the stage road and public highway leading directly from- the 
worst-infested portion of Sonoma, and on which vineyard material was, and 
is, constantly being hauled back and forth. It is plainly from this highway 
and its infested wagonloads that the insect has spread in the Napa Valley. 

The " spot " alluded to is believed by the writers to have been 
either in the old Squibb vineyard (10 acres), in the old McClure 
vineyard adjoining, or in the Callan vineyard (50 acres). All these 
were located close together. They have long since been pulled up, 
the land is now pasture, and only a very few of the old original 
vines still exist, although browsed down by the stock. These vines 
date back to 1866. 

From present knowledge of the biology of the phylloxera, it is be- 
lieved by the writers that the vineyard material referred to by Prof. 
Hilgard was responsible for the spread of the pest to this location, 
but the inoculation was due to the wandering young radicicole 
larvae rather than to the winged form. 

PHYLLOXERA SPREAD BY PICKING BOXES. 

" Vineyard material " may imply many sources of infestation. 
Besides rooted vines, grape-picking boxes are very likely to trans- 



10 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

port the insect from one district to another. At times grapes are de- 
livered to the wineries in greater quantities than can be handled, 
and boxes of grapes are unloaded and left at the winery instead of 
their contents being emptied into the elevators and the empty boxes 
returned to the same wagon. Boxes are exchanged, and some from 
infested districts find their way to uninfested vineyards. Wander- 
ing larvae (wanderers) easily shelter themselves in cracks and joints 
of boxes while these remain strewn throughout the vineyard waiting 
to be filled with grapes, and when the boxes are transferred to other 
vineyards, after having been emptied at the winery, the insects may 
be released by the shock of the empty box against the ground in 
the process of unloading. 

In their practical experience, certain grape growers have noticed 
that the first signs of phylloxera in their vineyards appear at places 
where they have been in the habit of dumping boxes for the con- 
venience of grape pickers. 

There were a number of wineries, reputed for the excellence of 
their wines, in the early-infested district around Glen Ellen, Sonoma, 
and Los Guillicos, and grapes were hauled to them from afar at 
about the time vines were dying rapidly in their vicinity. This 
accounts, no doubt, for the several early centers of infestation which 
appeared in a short period of time in Napa County. 

The pest spread into Napa County from Sonoma County not only 
along the highway to and beyond the vineyards cited in Prof. Hil- 
gard's report, but also over the ranges of hills referred to in the same 
report by means of a mountain road which ran over the divide from 
Sonoma and descended into a long narrow valley (Brown Valley), 
which itself opened out into Napa Valley quite close to the city of 
Napa. At the head of Brown Valley and almost on the county 
boundary line is the Dell vineyard. From the owner, Mr. C. Dell, 
the following information was obtained : In 1867, 20 acres of Mission 
grapes were planted with cuttings obtained from the Wing vineyard 
(then owned by Buhman Bros.), material for which formerly had 
been secured from the Buena Vista district at Sonoma. After seven 
years the Dell vineyard began to show signs of phylloxera in small 
patches, but bore good crops for four years. The Wing vineyard, 
located close by, began to die at the same time. 

The phylloxera was introduced in this case probably by means of 
picking boxes, or else by rooted vines planted to fill out places where 
the cuttings had failed. If the dates are correct, the infestation 
would have been noticed, without the cause being known, in 1874, or 
about the time it was discovered along the Sonoma highway. 

The above data are recorded to indicate how important a role this 
Sonoma Creek district played in the first introduction of the insect 
into California and how the spread occurred through different chan- 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 11 

nels. For this reason the early plantings give an idea of how the 
insect could have been spread before its presence was suspected. 

PRACTICAL METHODS EMPLOYED TO ARREST THE SPREAD OF THE PEST. 

When the discovery of phylloxera in California was first made 
known, the grape growers were already acquainted more or less 
with the havoc it had produced in the vineyards of France, and a 
panic spread throughout the different grape districts. It soon sub- 
sided, however, when the vineyards were not being rapidly destroyed, 
and even precautionary measures were overlooked. 

Of all the grape-growing counties, that portion of Alameda County 
known as the Livermore Valley district evolved the best organized 
system of quarantine measures, the aim of which was not to prohibit 
the importation of vines into the county, but to have cuttings, as 
well as rooted vines, thoroughly disinfected before they were per- 
mitted to be planted. 8 

The disinfectant used was a commercial soluble phenol. Vines 
were immersed for one-half hour in a solution of 1 part phenol to 60 
parts water. Notwithstanding these precautions, vines were intro- 
duced without the knowledge of the quarantine commission, and 
there occurred three distinct centers of infestation from which the 
pest was remarked to spread with the prevailing summer winds. 
Two of these centers were planted originally with material from 
San Jose, and the third with vines from St. Helena, in Xapa County. 

DISTRIBUTION OF PHYLLOXERA IN CALIFORNIA. 

As far as has been observed, Stanislaus, Merced, Kings, and Madera 
Counties, north of Tehachapi Pass, are free from phylloxera. South 
of Tehachapi Pass it has not been found so far. Most of the counties 
named have either enacted ordinances establishing prohibitive quar- 
antine against the importation of grapevines or protective measures 
subjecting vines to strict inspection and fumigation. 

The absence of infestation is without doubt not wholly due to 
quarantine measures, which were enacted years after the pest had 
many opportunities to be introduced, but more likely is due to the 
combined conditions of climate and soil in these counties. 

The writers have made a personal investigation of the present status 
of phylloxera infestation, and have tried to ascertain and estimate 
approximately the damage caused to the Agricultural interests. At 
this late date, however, there is much difficulty in obtaining informa- 
tion on which to base the estimate. Quite a number of vine3 r ards have 
been replanted, some as many as three times ; property has changed 
hands, and the history of vineyards has been forgotten. Again, 

8 Data personally contributed by Charles A. Wetmore, formerly chief executive of the 
State board of viticultural commissioners. 



12 



BULLETIN 903 U. S. DEPARTMENT OF AGRICULTURE. 



no traces exist of large vineyards pulled up but not replanted, 
and thus accurate data are unobtainable. Therefore a summarized 
statement based upon data to be found in the various reports of 




Fig. 1. — Map indicating progress of phylloxera infestation in California. The map does 
not show the severity or degree of infestation. Counties having less than 250 acres of 
vineyards were not inspected. In those counties marked douhtfully infested inspection 
took place at a time of year when the insect was difficult to detect ; none were found 
but the aerial growth of the vines suggested phylloxeration. In the counties of Kings, 
San Benito, Merced, Stanislaus, Calaveras, Amador, and Tehama no phylloxera was 
found at the time of inspection, but they should not he deemed to a certainty free of the 
insect. 

the State Board of Viticultural Commissioners and other agricul- 
tural and horticultural reports is presented. This, with the aid of 
a map of California (fig. 1) to indicate infested counties in shad- 



THE GKAPE PHYLLOXEKA IN CALIFORNIA. 



13 



ings to correspond to a period of years within certain dates, will 
enable one at a glance to conceive the degree of injury produced 
and the loss sustained by the viticultural interests. 

A general idea can be formed of the growth of the viticultural 
interests of California and correlatively of the economic importance 
of the grape phylloxera by comparing the report on grape produc- 
tion of the State statistician for the year 1914 with the report of a 
similar nature for the period 1856-1866 (Table I). 

Table I. — Planting of vines in California in different perods. 



County. 


Vines planted in — 


Total 

vines 

existing 

in 1865. 


Total 
bearing 

vines 
existing 
in 1866. 


Total 

vines 

existing 

in 1910. 




1856 


1857 


1858 


Alameda 


48,000 

9,000 

15,000 


125, 000 
8,000 

45,773 
6,465 
3,120 

34,468 


175, 000 
20, 000 
80, 707 
24, 187 

4,285 
42, 640 

1,056 
77,472 

3,000 
915 


1,575,000 

180, 000 

726, 363 

217, 665 

36,000 

383, 760 

9,450 

697, 248 

27, 000 

8,235 


. 155, 070 

757, 773 

369, 785 

515,049 

47, 800 

201, 518 

120 

1,441,039 


2, 390, 959 


Amador 


314, 604 


Butte 


258, 742 


Calaveras 


212, 300 


Colusa 


10,000 
75,000 


482,417 


Contra Costa 


2,972,130 


Del Norte 




Eldorado 


6,390 

2,000 

800 


26,400 

1,000 

500 


581,342 


Fresno 


40,687,207 


Humboldt 


839 

252 

2,917 

11,000 

200 

3,000,000 

11,542 

51,783 

100, 740 

84,839 

1,166,935 

124,000 

397, 101 

1,616 

951,315 

312, 562 

1,915 

75 

493, 387 

18, 263 

16,000 

220,000 

2,000,000 

218, 100 

1, 534, 520 

4,737 

8,469 

950, 600 

2, 830, 195 

112,310 

163, 663 

145,883 

19, 096 

100, 950 

505, 250 

157, 434 

494,472 


4,095 




39, 478 


Klamath 




1,000 


2,666 


18, 000 








296, 752 












31 


Los Angeles 


726,000 


600,000 

500 

15,227 

15, 000 

11,650 

55,000 

6,000 

5,742 

800 

119, 500 

38,000 

4,000 

1,200 

28, 640 

2,000 

40,000 

70,000 

500,000 

6,179 

6,100 

1,900 

1,000 

50,000 

170, 508 

3,020 

135,369 

2,000 

1,717 

400 

29,891 

61,903 

30, 000 


1,650,000 

600 

15,000 

15,000 

50,000 

90, 000 

8,000 

5,000 

400 

327, 900 

75,000 

50,000 

1,000 

40,000 

10,000 

40, 000 

90, 000 

513,000 

20,000 

25, 000 

3,500 

2,000 

52,869 

187,621 

1,800 

50,000 

5,500 

1,151 

30, 000 

57, 520 

155,425 

50,000 


14, 850, 000 

5,400 

135, 000 

135, 000 

50,000 

810, 000 

72,000 

45,000 

3,600 

2,951,000 

675, 000 

450,000 

9,000 

4, 112, 792 

90, 000 

360, 000 

810, 000 

4,617,000 

56, 000 

225, 000 

31, 500 

180, 000 

554, 178 

2, 000, 000 

162,000 

450, 000 

49, 500 

10,359 

270, 000 

517,734 

1,398,825 

450,000 


4,923,877 


Marin 


115, 198 


Mariposa 


1,000 
10, 000 
10,000 
22,700 


28,647 


Merced 


1,281,342 


Monterey 


79, 935 


Napa 


8,595,338 


Nevada , 


94, 338 


Placer 


2,702 


1,340,132 


Plumas 




Sacramento 


52, 200 

80,000 

4,000 


7,627,510 
987, 127 


San Bernardino 


San Diego 


1,228,858 


San Francisco 


3,000 


San Joaquin 


13,467 
1,500 
5,000 

15,000 

150,000 

5,000 

5,348 


13,371,794 


San Luis Obispo 


265, 481 


San Mateo 


124, 990 


Santa Barbara 


208, 595 


Santa Clara 


5,584,480 


Santa Cruz 


1,365,418 


Shasta 


117, 481 


Sierra 




Siskiyou 


1,000 
56, 178 
61,590 

4,420 
45, 123 


2,473 


Solano 


1,213,265 


Sonoma and Mendocino 

Stanislaus 


18, 864, 163 
1,932,302 


Sutter 


1, 249, 923 


Tehama 


1, 307, 218 


Trinitv 


150 


2,842 


Tulare -. 


7, 227, 491 


Tuolumne ' 


9,858 
26, 902 
28,000 


95,811 


Yolo 


2,568,019 


Yuba 


162,751 


Alpine 


9,000 


Glenn 












20,416 


Imperial 












298, 813 


Kern 












419, 582 


Kings 












4,538,732 


Madera 












795 


Modoc 












2,000 


Mono 












282, 682 


Orange 












1,570,794 


Riverside. . 












177, 976 


San Benito. . . 












1, 530, 630 


Ventura 












36,398 
















Total number of vines. . . 
Total acres 


1,540,134 


2,265,062 


3, 854, 548 
11,411 


40, 172, 654 
59,077 


19,695,814 
28,966 


139,099,560 











14 BULLETIN 903, U. S. DEPARTMENT OE AGRICULTURE. 

At this earlier period the pioneer growers of grapes were begin- 
ning to realize the possibilities of success due to the advantage of the 
peculiar suitabilities of climate and soil in California for the culture 
of European varieties of Vitis vinifera. 

Within the period of 48 years (1866-1914) there had been an 
increase of nearly 90,000,000 vines. Within this lapse of time, so 
comparatively short for such a prominent industry of the State, 
many changes occurred in the different viticultural districts with 
which phylloxera had little or nothing to do, and the gradual damage 
and loss caused by the insect could not be compared with the acutely 
sinister influence of extreme fluctuations in the market values of 
grapes, whether for wine, raisin, or table use, which swayed the 
industry at different times from opulence to ruin and vice versa for 
the growers; yet when looking backward over the years, the phyl- 
loxera stands out preeminent and is considered as the main single 
factor in the loss and damage sustained by California viticulture. 

In the early period the counties south of the San Bernardino 
boundary line were in the lead for the acreage in vines and for the 
production of wine. To-day in these counties viticulture is of sec- 
ondary importance, yet phylloxera has never been discovered there. 
The Anaheim disease was one of the causes of this decline, but the 
change to the more lucrative investments in citrus culture, which no 
doubt appealed more to the tastes of the many eastern settlers who 
largely populated that portion of the State, is mainly responsible for 
the falling off in acreage of grapes and lack of interest in the industry. 

Another viticultural district which underwent a great change was 
that of the Santa Clara Valley. There grape growing increased 
rapidly from 1885 to 1895, when the acreage of vineyards was the 
greatest and the county of Santa Clara produced almost one-third 
of the dry wines of the State. From 1893, when the vines began to 
die, the decline in acreage was much more rauid than had been its 
growth. 

It was commonly believed at the time that the Anaheim disease, 
which had caused such great ravages in the southern part of the 
State, was also responsible for the sudden dying off of the vines in 
the Santa Clara Valley. The damage caused to the vineyards was 
so extensive that an investigation was instituted by the College of 
Agriculture of the University of California to determine the 
cause (3). The general conclusions arrived at were the following: 

First, that the dying vines exhibit symptoms differing materially from those 
shown by the vines in Southern California which were destroyed by the Ana- 
heim disease; and, second that whether or not there be some "unknown in- 
fluence" at work, as suggested by Mr. Newton B. Pierce, the real, determining 
factor is the deficiency of rainfall during the years 1897-1900. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 15 

At this time the phylloxera was known to exist more or less 
throughout the valley, and had been identified in different vineyards, 
but as yet its injury had not reached the advanced stage of noticeable 
characteristic phylloxera spots, was therefore little in evidence, and 
was not considered a prominent factor in connection with the de- 
struction of the vineyards. 

The following facts were brought out during the writers' investi- 
gations and have a direct bearing upon existing conditions in the 
Santa Clara Valley at that time : 

Extensive areas of a vineyard may be infested by phylloxera be- 
fore characteristic spots are noticeable; a lighter crop and a slight 
decline in vigor of growth are for some time the only apparent signs 
of injury. 

Infested vines change suddenly for the worse, becoming rapidly 
stunted in growth, or even dying, when influenced by unusual con- 
ditions either from lack or excess of moisture. 

Injured roots, functioning poorly under normal conditions of 
moisture, reproduce with difficulty fibrous roots, or feeders, to replace 
those which have been destroyed by the insect, and when subjected to 
drought they starve the vine. 

Excessive moisture, instead of benefiting injured roots, causes them 
to rot and hastens the death of the vine. 

For these reasons it is believed that the phylloxera was responsible 
for a far greater share of the destruction of the Santa Clara Valley 
vineyards than has been ascribed to it. 

While Santa Clara and the southern counties have lost in acreage, 
a larger gain has been made at about the same period and later 
in other counties, especially those of Sutter, San Joaquin, and 
Fresno. Many vines throughout the State have been killed by 
phylloxera and not replanted; more have been grubbed out and 
replanted, sometimes more than once, and it is estimated that the 
loss in these respects has been very considerable. 

Mr. George C. Husmann, pomologist in charge of viticultural 
investigations, Bureau of Plant Industry, United States Department 
of Agriculture, estimates the loss at 75,000 acres; Prof. F. T. Bioletti, 
of the viticultural department of the University of California, makes 
a similar estimate ; and Charles C. Wetmore, for many years identi- 
fied with the board of State viticultural commissioners, considers 
this estimate conservative. 

VINEYARD DESTRUCTION. 

PROGRESS OF THE DESTRUCTION OF A VINIFERA VINE. 

According to conditions there is a great variation in the number 
of months or years that elapse between its original infestation by 



16 BULLETIN" 903, U. S. DEPARTMENT OF AGRICULTURE. 

phylloxera and the actual death of the vine. The following points 
have important bearing on this: 

Soil conditions and drainage. — From a survey made throughout 
the different districts of California, the following general statements 
can be made in regard to the destruction of vineyards when the vines 
are 8 to 10 years of age or older before becoming infested : 

Vines live longer in rich, deep, well-drained soils. Under such 
conditions, vineyards known to have been infested for 20 years and 
longer still bear crops, have only a few vines actually dead, and 
but a small percentage bearing little or no crop. 

Vines die sooner and the crop of the vineyard is more rapidly 
diminished in quantity and quality when established on rich soil 
only a few feet deep and with poor drainage, or on side-hill soils 
lacking moisture. 

Vines are still more rapidly affected in heavy soils, more or less 
shallow, with compact clay subsoil. In such types of soil, the vines, 
more or less stunted and enfeebled, may live a number of years. 
After a winter of unusually heavy rainfall they may show a very 
rapid serious decline or even a majority of them may die within a 
year. 

Vines growing in a well- drained, very loose, and friable sandy soil, 
or one with a surface of blow sand several inches in depth, seem to 
be almost immune to the attack of phylloxera. 

As a sandy soil becomes heavier in texture and of poorer drainage, 
so the vine succumbs more readily to the attack of the insect. 

Age of vine at infestation. — Young vines are destroyed more readily 
during the first three years, before they have established a fairly 
good root system. When vines are 8 or 10 years old the quality and 
texture of the soil become main factors, and the more or less rapid de- 
struction of the vineyard depends on the adaptation of the vine to 
the soil and the advantages of prolification and diffusion for the 
insect. The general experience has been as follows: 

Cuttings infested in their early growth rarely survive the first 
year. 

Rooted vines, infested from the time of planting, produce from the 
start a very poor vineyard, which rarely lasts more than three or four 
years, the individual infested vines living after infestation hardly 
more than two years. If vines become infested during the second 
or third year from planting, they may last longer if they have 
a good root s}^stem, and in this case the vineyard may produce one 
or two crops smaller than normal and perhaps last five or six years. 
When a vine is three years old or more before infestation, its longev- 
ity depends somewhat on variety, much more on age, and especially 
on soil conditions. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 17 

Too few American varieties, either nonresistant or resistant, are 
grown in the State of California at this time to have been con- 
sidered in this investigation. 

Intrinsic vigor of vines. — Vines of great intrinsic vigor always re- 
sist phylloxera attack better than naturally weak plants. 

Varieties of vines. — Amongst vinifera varieties grown in Cali- 
fornia, a few have shown certain resistance when inoculations have 
taken place several years after planting. Such are, in order, Flame, 
Tokay, Mission, and Muscat (Fresno district), and in a lesser degree 
Grenache, Chasselas, and Burger. Laboratory tests with certain 
varieties in which phylloxera lesions rotted rapidly have shown that 
Zinfandel, Thompson's Seedless, Carignan, Burger, and Muscat suc- 
cumbed more rapidly and Tokay and Grenache less rapidly. 

Destruction of a highly susceptible vine. — Under favorable con- 
ditions for rapid phylloxeration, the hypothetical progress of de- 
struction of a highly susceptible vine, as Zinfandel, with established 
roots may be set down as follows: During summer and fall a few 
larvae settle on a part of the root system; the following year in- 
festation spreads to the surface fibrous and fleshy roots, and to a 
certain extent to the large roots near the crown, and nodosities and 
tuberosities are formed. The third year the subterranean infesta- 
tion spreads pretty well throughout the root system, although it 
is rare to find year-old wood much attacked, for it appears that 
the habit of roots of this age to slough the outer layer of bark pre- 
vents the phylloxera? from retaining a hold, and compels those 
already settled to move to other more hospitable portions of the root 
system. In this year some of the larger roots decay under combina- 
tion of phylloxera attack and excessive moisture in the subsoil or 
become dried out from phylloxeration combined with too great 
drought, and thus the flow of sap between the feeding rootlets and 
the aerial portion of the vine is more or less cut off. This results 
in a shortening of cane growth and sometimes in an abnormally 
large crop of grapes. During this third summer as the larger roots 
die an emigration of young larvae takes place. Many winged forms 
also may be developed. The fourth year finds the larger roots in 
great part destroyed, the cane growth correspondingly reduced, and 
a large number of fibrous and fleshy rootlets sent out from the 
trunk just below the soil surface. The phylloxera? colonize these 
rootlets in spring, but leave them in summer, when they decay. There 
is also a heavy migration from the decaying roots farther down 
in the soil. In the autumn it is hard to find phylloxera on such a 
vine, and this explains the maxim that the best type of phylloxerated 
vine On which to look for the insect is not one badly stunted, but 
rather one with slight stunting of the Canes; in fact, one in the 
1900°— 21 2 



18 BULLETIN 903, U. S. DEPARTMENT OE AGRICULTURE. 

second or third year of phylloxeration. Such a vine as has been 
portrayed generally dies in the fifth or sixth year from the initial 
attack. 

As has been pointed out above, the decline of a vine is influenced 
by many conditions, and the hypothetical case given shows the mini- 
mum longevity of an established susceptible vine after phylloxeration. 
Under favorable conditions infested vines live much longer, and in 
extreme cases their length of life seems hardly affected by the con- 
tinued presence of the insect on their roots, a slight decrease in the 
size of the crop being the only evidence of injury. 

HOW THE PRESENCE OF PHYLLOXERA IS INDICATED. 

The existence of the phylloxera in a vineyard is indicated by the 
well-known areas or " oil spots," so termed because 01 their man- 
ner of spreading. A " spot " appears first in the form of one or 
two vines showing a slight shortening of the canes and a premature 
seasonal yellowing of the leaves, although the latter symptom may 
be caused by the red spider (Tetranychus bimaculatus Harvey), or 
by alkali in the soil. The year following this indication the vines 
originally infested exhibit a more noticeably stunted appearance, 
while other vines surrounding them show slight shortening of canes 
and premature discoloration of foliage. After this the "spot" in- 
creases in size, in course of time the vines in its center die, and 
finally the vineyard may become totally destroyed. The writers have 
never observed the " spots " to increase as rapidly in California as 
they are reported to have done in the vineyards of France after the 
time the insect first reached that country, when 2,500,000 acres were 
destroyed in 25 years, and vineyards frequently have been observed 
in California which had phylloxera " spots " of more than 20 years' 
standing to have vines still living. 

The " oil spot " generally is circular in shape, but sometimes it 
assumes other forms. At times it is oval or narrowly elongate, the 
latter form occurring on hillside vineyards through which water 
rills run in the spring. In such cases spread of the " spot " is often 
rapid in a downward direction, indicating that running water is 
an extra factor in the spread of infestation. The writers have 
demonstrated by experiment (see " Diffusion of phylloxera," p. 100) 
that the phylloxera can be carried in water from one vine to another, 
and when the rains of March and April occur there are plenty of 
active phylloxera on the roots. In other cases the spread of a " spot " 
follows the direction of the prevailing winds and it appears that this 
spread is caused by wind agency in the transportation of wandering 
larvae in summer and autumn. In vineyards where vines are planted 
rectangularly (i. e., 8 by 12 feet), instead of square, the infestation 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 19 

very frequently spreads along the shorter 8-foot rows, indicating 
that the insects traverse more easily the shorter than the longer dis- 
tances. Aerial and subterranean migrations of wandering larvae 
play an important part in the enlargement of phylloxera " spots." 
Only an infinitesimal percentage of the thousands of wandering 
larvse succeed in reaching their goal, but, as they are parthenogenetic 
radicicoles, a single larva can cause a new infestation or start a 
new " spot " at quite a distance from the original one, either in the 
same or in another vineyard. 

The estimation of root injury from external appearance usually 
can be made with considerable accuracy, and the degree of infesta- 
tion of a vineyard computed by the number of "spots," their size, 
and the stunted condition of the vines composing them. 

The diagrams (figs. 2 and 3) indicate a phylloxera " spot" charted, 
respectively, in the years 1914 and 1915. This " spot " occurred on a 
heavy black clay soil on a hillside of moderate slope. It appeared 
that the " spot " started about the year 1907 when the vines were 3 
years old, and that the first vines died about 1911. Surveys of the 
"spot" were made October 13, 1914, and November 5, 1915, and the 
vines were designated in the following manner : Ten was given to 
vines which showed no external evidences of phylloxeration ; 9 to 
those which showed very slight evidence, such as premature yellow- 
ing of foliage and slight shortening of canes; 8 to those showing 
more advanced symptoms of phylloxeration, and so on down to 1, 
which was given to vines which showed only the most feeble vegeta- 
tive growth. In order to portray the " spot " more vividly, symbols 
have been utilized as follows : Healthy vines, H ; vines designated 9 
and 8, S ; vines designated 7 and 6, / ; vines designated 5 and 4, U ; 
vines designated 3, 2, and 1, D ; vines killed by phylloxera, solid dot. 
In this vineyard every fourth vine had been replaced by a walnut tree, 
and these places where vines have been pulled out and not replaced 
are left blank in the diagrams. 

In the diagrams not all the " spot " is shown, for it has extensions, 
the principal one being on the north side across a 24-foot avenue and 
continuing down a swale for some 60 feet. Enough of the " spot " 
is shown to indicate its general form. Between 1914 and 1915 there 
occurred an unusually wet winter and the " spot " grew considerably 
in the 12 months between the surveys. Although the number of dead 
vines increased only from 43 to 49, and among the badly stunted 
types not much increase was shown, there was a marked increase in 
the number of vines showing recent phylloxeration. 

When more than one variety of vine is included in a " spot," a 
good index of the resisting power of the several vinifera varieties 
frequently is observable. Among the dead or moribund vines of 



20 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

the susceptible varieties stand out the more vigorous vines of the less 
susceptible kinds or even individuals of the same variety. 

• 

H H H S S S S H H 
H H S H S S H H S H H H 
S H H H H H S H H H H H H 
S HSH SHH S H H H 
SHHHSHHSSSSHSSHH 
HSJSHSSSHSHHHSSS 
SHSSHHHHSSIISSSSHH H 
H H S S HSH 11/ S S S U 

HHHSHSHSSSSSS>I I H S I S I U S 
H H H SSSSHHSHSSHSSIISS S 
HHHHHHSSISSSSHSSSSSSH S 
HHH HHS SSI SHS SSS S 
HHHHHHSSSSISSSSISISSH I 
HHHHHHSSSISSI%DIISSSH H 
HHHHHSSS>SS%DDDDUDUSSS S 
H H H H S S /•• ••• BUS S 

HHSHSssiDmmmmmmmui ssh h 

HHSHSIDD**D*%D%D U I S S H 

HssisuummummmmmDuussH 

S H S III • D • • • • /// H 
HHSHSSIII+Dm%D%UISSHH 

H H H H S I I I I I U m • • D I I S & H H 
HHHHHSSSISIUD%IISSHHH 

H H H H S I 1ST U I U SHH H 

H S H S H S S I S U I U I I I S S S> H H H 

H H H H S S S S I %%*USSHSHHH 

S H H H H H S S S I I % I S S H H H H H 

H S SSS U U S H H H 

H Healthy S H S H U I I I S S S H H H H 

S Slight infestation S S IS ISSSHHHSH 

I Inffstfd S'SSHHSHHHSH 

U C/a/hf/ilth/ SSS SSS 

D Dy/m S H S H H S S 

• Dfad H 

Pig. 2. — Phylloxera "spot" in Zinfandel vineyard, charted in 1914. (See tvxi.) 

The year previous to showing a marked decline, vines frequently 
bear an unusually abundant crop of grapes, and stunted vines seem 
to produce a larger amount of grapes in comparison to the size of 



Bui. 903, U. S. Dept. of Agriculture. 



Plate I, 




Fig. 1. — Young raisin vineyard uninfested by Phylloxera. 




Fig. 2. — Old vinifera vineyard infested throughout with Phylloxera and showing empty spaces 
where vines have been killed; vine in foreground shows less infestation by Phylloxera than 
others near by, and would be rated at 7, but the canes show obvious stunting. 

The Grape Phylloxera in California. 



Bui. 903, U. S. Dept. of Agriculture. 



Plate II 




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Bui. 903, U. S. Dept. of Agriculture. 



Plate IV. 




The Grape Phylloxera in California. 

Phylloxera vitifoliae: Fig. 1.— Phylloxera nodosities shown on Zinfandel grapevine: 
a, Nodosities on terminal rootlets; fr. nodosity showing Phylloxera feeding ;c,aaul1 louse; 
(I, molted skin of same. Fig. 2. — Phylloxera tuberosities on smaller root: a. Infested 
portion of root ; b, normal portion of root. Fig. 3.— Section o r . grapevine root showing 
adul I louse with eggs in situ. Fig. -1.— Sections of root infested: a, Newly formed tuber- 
osil v; b, advanced stage of tuberosity: C, side view of older form of tuberosity; (/. tuber- 
o^it y causing the cracked condition of bark; (, young colony of insects as found on roots. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 21 

their wood growth than do healthy ones. Such grapes mature, how- 
ever, without attaining a good size or their normal saccharine con- 

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Fig. 3.— Phylloxera "spot" in Zinfandel vineyard, charted in 1915. Same "spot" 
as shown in figure 2. (For description see text.) 

tent. Stunted vines produce leaves of a more uniform size than 
healthy vines, and because the internodes of the canes are shorter, 
the leaves appear more closely grouped, giving the "cabbage-head" 



22 BULLETIN 003, TJ. S. DEPARTMENT OF AGRICULTURE. 



appearance to the vines. Scarcity of rapid-growing terminal shoots 
and absence of tendrils are characteristics of stunted vines. Plate 
I, figure 1, shows a young vineyard which is uninfested and in which 
the vines have made normal growth. Plate II shows a small phyl- 
loxera "spot" in an old vineyard, the photograph showing stunted 
vines in the foreground. Plate III and Plate I, figure 2, indicate 
badly infested old vineyards, in which all the vines are phylloxe- 
rated and most of them badly stunted. The vine in the foreground 
of Plate III is obviously stunted, although less so than its neighbors. 

PHYLLOXERA ROOT LESIONS. 

Root lesions are swellings on grape roots caused by the puncture 
of the phylloxera beak. They are of two types, (1) nodosities and 
(2) tuberosities. 

The nodosity. — Nodosities (PI. IV, fig. 1) are rapidly growing 
swellings on the white fleshy feeding rootlets. They soon acquire 
a characteristic greenish-yellow color, and curve and bulge around 
the phylloxeras responsible for their inception so that the insects 
come to lie in a depression (PI. IV, fig. 1, b). A nodosity may be- 
come as much as six times the diameter of the normal size of the root 
when several insects have settled upon it, and about twice the di- 
ameter for a single occupant. Through its size, form, and color, 
the nodosity is very conspicuous in comparison with the root and is 
manifest proof of the presence of the phylloxera. 

In most cases the formation of a nodosity arrests the growth of the 
rootlet. At times the rootlet grows one-fourth inch or so in length, 
and occasionally the puncture of the phylloxera does not affect the 
rootlet in its growth, the subsequent swelling acquiring a lignous 
character and becoming a tuberosity. Nodosities are generally short- 
lived, lasting about a month. Excess moisture hastens their decay, 
lack of moisture dries them up, but a low, even temperature causes 
them to last longer. 

The foregoing also applies to the American variety of vines styled 
nonresistant. On the rootlets of the resistant American vines the 
phylloxeras frequently fail to cause swellings, and when nodosities 
are produced they are smaller, less fleshy, and brown in color. At 
times, though no swelling occurs, the rootlet dies at the point of 
puncture. 

The tuberosity. — Tuberosities (PL IV, figs. 2, 4) also are swellings 
caused by the puncture of the aphid. Though of a similar nature, 
they differ from nodosities in form because of the lignous character 
of older roots. They occur on all parts of the root system of vinifera 
vines except at the apex of the growing fibrous rootlets. They may 



THE GRAPE PHYLLOXERA 1ST CALIFORNIA. 23 

also occur on the trunk of the vine, both above and below the soil 
surface. They are less commonly formed on roots of one year's 
growth than on older wood. On resistant vines tuberous swellings 
are normally quite unusual, but they may be formed on the healing 
growth of the cambium layer about an abrasion. On most American, 
vines of nonresistant type, tuberosities are abundantly formed. On 
viniferaX resistant hybrids the more the resistant strain predominates 
the scarcer are the tuberosities. 

Tuberosities are formed at any time between March and October, 
most abundantly during the summer months. They are formed more 
readily on vigorous roots than on those somewhat dried or decayed. 
Hibernants often choose tuberosities upon which to pass the winter, 
besides inducing their growth at points as yet sound and uninfested, 
the mere insertion of the beak being sufficient to stimulate growth. 
Tuberosities vary considerably in their general appearance, even 
on the same vine. Some are minute papillae on the surface of 
the root. Others are large, fleshy, rapidly growing, globular out- 
growths, as much as half an inch in diameter, and this type is found 
chiefly on the smaller roots. Others are enlargements of the girth 
of the root at intervals, a type also confined to small roots. Others 
consist of more or less uniformly rounded swellings of one-sixth 
to one-fourth inch diameter on the root surface, and these are the 
ones most commonly found on larger roots. Such tuberosities by 
their growth generally split the epidermis of the root longitudinally, 
and as the split tends to lengthen at both ends, the tuberosity assumes 
an oval or elongate shape. Later, when the split enlarges, fresh 
tuberosities are formed by aphids on the inner layer of bark exposed 
by the split, and shortly a chain of lesions occurs along the crack. 
These cracks lengthen and often involve a length of more than 6 
inches. On roots growing horizontally or almost parallel to the soil 
surface, the majority of the tuberosities will occur on the lower side, 
the insects apparently settling there because of the greater moisture. 
On vertical or sloping roots tuberosities occur more or less uniformly 
all around. As long as they remain fresh, tuberosities provide an 
excellent quality of food for the aphids. This condition should be 
distinguished from the rapid development observed in the case of 
aphids settled on root callus, which forms at the point of severance 
and is caused by the action of the healing cells of the cambium layer 
becoming greatly enlarged and very fleshy, furnishing excellent 
food for the aphids, through the natural function of the wounded 
root. 

Many factors influence the length of existence of tuberosities. In 
general, it is found that those formed in the autumn will last until 
the rainy season, and commence to decay immediately afterwards. 



24 BULLETIN 903, TJ. S. DEPARTMENT OF AGRICULTURE. 

Their decay is expedited by a heavy rainfall and a high-water table. 
Those formed during the spring and summer in a moist environment 
rarely persist fresh beyond two months, and most of them decay 
about one month after they arise. It has been repeatedly observed 
how quickly a fresh tuberosity decays when it is placed against wet 
sand, and if a stream of water finds its way down a root the tuberosi- 
ties thereon start to decay immediately. On the other hand, they 
are more capable of withstanding dry soil conditions than are the 
nodosities, and under conditions approaching drought, which some- 
times occur in late summer and autumn, may last for a considerable 
time and even lignify, the dry environment having caused the insects 
settled on them to seek more favorable conditions of moisture and 
at the same time having kept in check decomposition. Tuberosities 
withstand a considerably greater range in temperature than do 
nodosities, and they are not affected by sudden changes in tempera- 
ture in the same manner as are the nodosities. 

Tuberosities grow larger and more rapidly in proportion to the 
soundness of the roots. On roots previously uninfested the growth 
of the swellings is rapid and vigorous, and a root, after it has been 
heavily phylloxerated for several months, becomes so greatly ex- 
hausted that it can not respond to the punctures of the aphids by 
developing new swellings, and the phylloxerse that are not gradually 
driven away to seek more nutritious food develop on the root without 
causing swellings. The decay of the tuberosities begins at the place 
first punctured by the aphids, generally at about the center of the 
swellings. The tuberosity forms around the insect, and decay is 
first evident as a small, blackened spot, sometimes exuding a liquid. 
The rapidity of decay of tuberosities is in proportion to the increasing 
moisture content of their environment, and in an unusually dry 
environment they frequently will lignify without causing the tissues 
to rot. Under moist conditions the inflated cells rapidly break down 
and decay usually spreads, and fungi and molds enter the tissues, es- 
pecially in the case of large bulbous swellings. Decay finally drives 
off the aphids, but through their stimulating action they are often 
able to retain the freshness of a tuberosity for some time after it 
has been surrounded by decayed tissues, and occasionally a fresh, 
vigorous specimen is found on a root otherwise quite decayed. The 
nutritious quality of these tuberous lesions provides for the* produc- 
tion of nymphs in great numbers. 

HOW ROOT LESIONS AFFECT THE HEALTH OF VINES. 

It has been shown in the foregoing pages that the nodosities are 
those phylloxera lesions formed at the apex of growing fibrous root- 
lets, whereas the tuberosities are lesions formed on all other parts 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 25 

of the root system. Since the vine derives its plant food through 
the growing rootlets that thrust their way through the soil, it is 
obvious that when such rootlets rot as a result of the decay of the 
nodosities situated on them no more sustenance can be afforded 
the plant through this medium. If, on the other hand, the rootlets 
continue to grow notwithstanding the nodosities situated on them, 
and if the nodosities lignify, the supply of nourishment provided by 
the rootlets is not cut off, and the nodosities become in effect tuber- 
osities. This is often the case with resistant vines, and much more 
rarely with vinifera or nonresistant Americans. In resistants these 
tuberosities generally lignify and heal, but in the other types of vines 
they do this only if their environment is quite dry. Nodosities effec- 
tively destroy the terminal rootlets; but since the insects spread 
very slowly on resistants, a vine of any vigor has abundant feeders, 
and thus it follows that resistant vines bearing very few or no tuber- 
osities, but having many nodosities, do not succumb to phylloxera. 
Resistant vines never lack the power to produce enough feeding 
rootlets to sustain them as long as the following conditions, which 
are normal to these vines, obtain: (1) When the development and 
spread of the phylloxera? on them are comparatively slow; (2) when 
a large percentage of insects that have been raised on the nodosi- 
ties become nymphs and later leave the roots as winged migrants, 
in an endeavor to reach the surface of the ground or the aerial 
parts of the vines. Both of these conditions may be affected by the 
quality of plant food, as will be shown. Instances have been seen 
in which young resistant vines have been rid of their entire infesta- 
tion because all of the immature phylloxera? became winged migrants 
in the autumn, but in the majority of cases of infested resistant 
vines under observation there remained in late fall a small wingless 
infestation, and in some instances where the vines had been growing 
in small pots with insufficient nourishment infestations of wingless 
aphids persisted, and the production of winged migrants during the 
autumn was proportionately small. These wingless infestations, 
however, were not prolific. It appears that thrifty resistant vines 
afford poor nourishment for phylloxera?, and they do not respond to 
phylloxeric irritation by producing swellings. When, however, re- 
sistant vines become weakened through a poor supply of plant food, 
the phylloxera? attacking them persist and the vines respond to the 
phylloxeric irritation and form lesions. 

Although the decay of the nodosities on vinifera vines destroys the 
feeding rootlets, this in itself is not a potent factor in the destruc- 
tion of the vines by phylloxera. Except under abnormal conditions, 
such as the confinement of vines in pots with impoverished soil, no 
case has ever been observed in which the death of a vine could be 
attributed solely to the decay of nodosities, whereas instances have 



26 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

been observed wherein vines flourished with their vitality but 
slightly impaired, notwithstanding a nodositous infestation extend- 
ing over several years. One such instance was that of a 20-year-old 
vineyard of Burger and Chasselas (viniferse) near Napa, Calif. 
In 1913 the vines had been phylloxerated for upward of eight years, 
and each year the nodosities had been extremely abundant and prac- 
tically no tuberosities had been developed, yet the vines appeared 
quite thrifty, owing to the maintenance of a sufficient number 
of uninfested feeders. It is the decay of the tuberosities on the 
larger roots, which the vine can not replace, that causes at first the 
impairment of the vine's functions and later results in its death. 
The simultaneous decay of many tuberosities is the cause of rapid 
decline in the vigor of a vine and is the prelude to the vine's death. 
The larger roots near the crown of the vine are especially susceptible 
to tuberositous decay, while the decay of a root below the crown 
is often very slow. This lower portion under favorable conditions 
is able to maintain itself undecayed for months, if not years, and is 
capable of providing nourishment for phylloxera. It is frequently 
observable that vines retain their vigor despite a ring of decay at 
the crown of the roots, and do not become stunted until the major 
portions of the larger roots have rotted. 

In a discussion of the effect of root lesions on the health of vines, 
emphasis should be placed upon the decay of the tuberositous le- 
sions and upon the fact that this decay is invariably hastened by 
moisture and retarded by dryness. Decomposition is often hastened 
by the work of fungi, molds, thysanurans, and tyroglyphid mites. 
The most common mite so working is Rhizoglyphus elongatus Banks, 
specimens of which were determined by Mr. Nathan Banks. It is 
a rather large species and is very prevalent throughout the grape 
sections of California. It was frequently reared on decaying roots 
kept in the cellar of the laboratory. The mite is hyaline white, 
with two brown circular spots, one behind the other, on the dorsum 
of the abdomen. 

NOMENCLATURE AND SYNONYMY OF THE GRAPE PHYLLOXERA. 

The genus Phylloxera was erected in 1834 by Boyer de Fons- 
colombe (10). The type species is P. quercus de Fonscolombe. In 
185G Asa Fitch (9) described the grape-leaf gall louse as Pemphigus 
vitifoliae. The species was obviously placed in the wrong genus. 
In 18G7 Shimer (21) erected a new family (Dactylosphaeridae) and 
a new genus, Dactylosphaera, for a new species of his {globosvm) and 
tentatively placed vitifoliae Fitch in this new family and genus. In a 
footnote he also proposed the genus Viteus for Fitch's insect. In 1868 
Planchon (20) described the grape root louse from France as Rhyz- 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 27 

aphis vastatrix Planchon, and in the same year Signoret (22) placed 
the species vastatrix in the genus Phylloxera de Fonscolombe. The 
year following Westwood (23), in England, described the insect as 
Peritymbia vitisana, but in a later article the same year he placed 
his species in synonymy as follows : Peritymbia vitisana Westwood = 
Pemphigus vitifoliae Fitch, D actylosphaera (?) vitifoliae Shimer, 
and Phylloxera vastatrix Planchon (19). Until 1900 the name gen- 
erally recognized by writers had been Phylloxera vastatrix Planchon. 
In 1900 Del Guercio (12), in Italy, erected the genus Xerampelus to 
receive the grapevine species, which he therefore called Xerampelus 
vastator. This genus has not been recognized by all later authors. 
Grassi (11, p. 12) would retain Shimer's proposed genus Viteus as a 
subgenus to Phylloxera, and would thus name the species Phylloxera 
(Viteus) vastatrix. The present writers are inclined to retain the 
specific name vitifoliae Fitch on account of its evident priority over 
Planchon's more widely known vastatrix, and notwithstanding the 
objections raised by authors as to its orthographical correctness 
(vitisfolii and vitifolii have been preferred and written). As to the 
generic title, it has been decided that Phylloxera will be retained, 
the question of the subdivision of the genus being left to those who 
have had more opportunity to study the specific ramifications of 
this group. 

The synonymy of the grape phylloxera as understood by the 
writers is therefore as follows : 

Phylloxera vitifoliae (Fitch). 

Pemphigus vitifoliae Fitch, 1855-56. 

D actylosphaera (?) vitifoliae (Fitch) Shimer, 1867. 

Viteus vitifoliae (Fitch) Shimer, 1867. 

Rhyzaphis vastatrix Planchon, 1868. 

Phylloxera vastatrix (Planchon) Signoret, 1868. 

Peritymbia vitisana- Westwood, 1869. 

Xerampelus vastator (Planchon) Del Guercio, 1900. 

Viteus vastator (Planchon) Grassi et al, 1912. 

BIOLOGY OF THE GRAPE PHYLLOXERA IN CALIFORNIA. 

THE LIFE CYCLE. 

The complete life cycle of the grape Phylloxera under natural con- 
ditions, i. e., on the wild vines of eastern North America, is extremely 
complicated (fig. 4). It is not the intention of the authors to enter 
into all the ramifications of this cycle in the present paper, but it 
may be said that the following are the main forms that occur: (1) 
The stem mother or fundatrix, which hatches in spring from the 
winter egg, ascends to an early leaf, settles on the upper surface, 
and causes to form around her a pocketlike gall opening on the 



28 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

A/ 




Fig. 4. — Phylloxera vitifoliae: Genealogical graph of the grape phylloxera in the eastern 
part of North America and in tho Mediterranean regions. A, Hibernant radicicole : 
B—O, successive radicicole generations ; H, winged sexuparous migrant ; I, sexes ; 
J, stem-mother gallicole ; K-P, successive gallicole generations, part of the young larva* 
of which proceed below ground (Q) to join the radicicole circle* at various stages de- 
pendent upon the gallicole generation of which they were members ; Z, emergence above 
ground of the wandering radicicole larvae. In this figure, in order to avoid undue con- 
fusion, no account has been taken of the development in the stalls of winged sexuparous 
migrants. Such development is unusual, but it indicates the possibility of a lift 1 cycle 
entirely aerial. 



THE GEAPE PHYLLOXERA IN CALIFORNIA. 29 

upper side of the leaf; (2) several parthenogenetic generations to 
which the stem mother gives rise, some of which settle on the foliage 
and produce new galls, as gallicoles, while others repair to the roots 
and settle on them as radicicoles; (3) parthenogenetic generations 
on the roots descended from the phylloxeras which went from the 
foliage to the roots; (4) winged migratory forms, comprising a very 
variable percentage of the root and gall forms, produced in summer 
and autumn, which fly or are transported by wind to other vines and 
oviposit either under the bark or on the leaves; (5) the true sexes, 
which are wingless and beakless; (6) the winter egg, deposited under 
the bark by the sexed female after coition; (7) radicicoles, born on 
roots in the late autumn, which pass the winter thereon as small 
hibernants, mature the spring following, and give rise to radicicole 
generations which succeed one another during the summer and 
autumn. This, briefly, is the life cycle that occurs in parts of 
Europe where American vines are used for stock, and in the eastern 
and southern United States on the wild grapes and on varieties de- 
rived from them. 

It will be observed that the winter may be passed in two forms — 
the winter egg and the hibernant, the former on the aerial and the 
latter on the subterranean or root portion of the vine. On certain 
wild grapes, as Vitis riparia, V. rupestris, and V. herlandieri, and on 
hybrids from these species, the former is the normal form, and hiber- 
nating larvae are rare. On species like Vitis labrusca, V. monticola, 
and their derivatives, both forms may occur. On viniferse (Vitis 
vinifera) the latter form is by far the more common. In the 
majority of European grape districts both forms occur, the former 
on American resistant vines and the latter on viniferse, but in other 
localities, even where resistant vines are used, the winter egg is very 
scarce. These include certain regions of France and California, and 
it appears that in California the hibernant is normally the only form 
that passes the winter. 

The suppression of the winter egg, and, therefore, of the succeeding 
gall form, brings about a modified life cycle in the California vine- 
yard which may be briefly described as follows: (1) The hibernant 
radicicole passes the winter as a larva on the roots and occasionally 
on the trunk beneath the bark. (2) The hibernant, when mature, 
gives rise to generations of radicicoles, and the aphids that issue 
from eggs in late autumn become hibernants. (3) A certain per- 
centage of radicicoles, varying from causes such as humidity, tem- 
perature, condition of food, and variety of vine, develop into winged 
migrants and issue from the ground. (4) Radicicole larva? forsake 
the roots and seek to reach other vines either by way of the soil 
surface or through subterranean passages such as cracks. 



30 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



The part of the life cycle from the sexes to the gallicoles through 
the winter egg and fundatrix is either omitted or does not proceed 
beyond the winter egg in California, notwithstanding the frequent 




Fig. 5. — Phylloxera vitifoUac: Genealogical graph of tlio grape phylloxera in California. 
A, hibernant radicicole ; B-O, successive radicicole generations ; H, winged sexuparous 
migrant; I, sexes; Z, emergence above ground of the wandering radicicole larvse. 

abundance of resistant types of vines, types many of which normally 
bear galls in other localities. The result is that the California cycle 
(fig. 5) is purely parthenogenetic and is therefore greatly modified 
from the original cycle (fig. 4) occurring on wild vines, the natural 
hosts of the insect. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 31 

RESUME OF LIFE HISTORY IN CALIFORNIA. 

A resume of the life history will be presented before all the dif- 
ferent stages and habits of the phylloxera in California are discussed 
in detail. This resume is confined to the biology of the insect on 
viniferae and does not consider the life history on resistant roots. 

Over 99 per cent of the phylloxerae pass the winter as small brown- 
ish unmolted larvae, the remainder hibernating after having passed 
one or two molts. All parts of the root system are used for hibernat- 
ing quarters, but the majority cluster on the larger roots, following 
an upward migration in the fall. 

Coincident with the first sap flow in early spring is the growth of 
the hibernants, but in a given vineyard the earliest individuals com- 
mence to grow fully six weeks before the most tardy ones, so that 
after the foliage has opened, hibernating larvae are still to be found 
on the roots. The development of the hibernants is considerably 
slower than that of the summer broods, and the former mature on 
the average about five and one-half weeks after they commence their 
spring growth. The development of the larvae is at all times influ- 
enced by the quality of food and by conditions of humidity and 
temperature. 

Upon casting its fourth skin, the hibernant is mature and com- 
mences egg deposition. Its progeny are the first-generation phyl- 
loxeras, and these on hatching from the eggs either settle beside the 
eggshell or go in search of new food. Many aphids settle on young 
growing rootlets and produce the fleshy swellings, termed " nodo- 
sities." Others settle upon older roots and produce swellings, termed 
"tuberosities." Still others develop on roots without causing the 
development of either perceptible swellings or lesions. Individuals 
feeding upon nodosities develop more rapidly than do those on the 
unswollen surface of the root. The nodosities usually decay within 
a few weeks after their formation, and in most cases the destruction 
of the rootlets follows. The tuberosities also usually decay in time. 
The rotting of the nodosities is not very serious, as the vine can 
supply new apical growth, but the decay of the tuberosities leads to 
the decay of the larger roots either wholly or in part, and as a result 
the vitality of the vine is greatly impaired, or the vine is killed 
outright. 

The first-generation individuals are mature in from four to seven 
weeks after the eggs have been deposited, and they in their turn 
deposit eggs, which produce further generations throughout the 
summer and autumn. 

Owing to the fact that, under favorable conditions, the adults 
deposit eggs during an average period of 45 days, an overlapping of 
generations ensues during the summer and fall. In order to avoid 



32 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



confusion, it is assumed that there are five generations annually, 
since this number is about the average in a vineyard in which the 
sap moves early, although there might be, under certain conditions, 
from one to eight or even nine generations within a single year. 
The hibernant generation having matured in April, the succeeding 
generation matures about the time the canes have ended their first 
rapid growth, approximately the end of May. Succeeding genera- 
tions mature on about the following average dates : Second, July 6 ; 
third, August 15 ; fourth, September 30 ; the fifth generation hiber- 
nating. 

A variable percentage of the larvae of generations 2, 3, and 4 
becomes nymphs, and these later emerge from the ground as winged 
insects and either fly away or are borne off on the wind. Large 
numbers of these are caught in spider webs. Many of the newly 
hatched larvae develop a wandering tendency just after they have 
issued from the eggshell and seek to emigrate to other vines either 
through the soil or over the surface of the ground. Large numbers 
of these migrating larvae are also caught in spider webs on the surface, 
and while only a small percentage reach their destination, a single 
individual may start a new infestation. Those of the larvae that suc- 
ceed in fastening upon a root or rootlet develop as radicicoles. 
The winged forms normally occur from June to October, and the 
wandering larvae are found from July to September. 

During July and August, when the adult radicicoles are most 
prolific, incubation and development proceed most rapidly, and the 
phylloxera may be said then to have reached its most active stage. 
It is at this stage that the greatest damage is done to the roots of the 
vines, although the effects are not generally apparent until the fall 
and winter following, when the lesions formed during the summer 
have decayed. 

At the end of September a few of the newly hatched larvae 
hibernate, and throughout October successive generations become 
hibernants, so that by the end of the month a large majority of the 
phylloxera have reached this stage. During November and the 
first half of December, a few mature radicicoles and growing larvae 
may be found, but after the middle of December, it is unusual to 
find any form but the hibernating larva. 

Under conditions of abundant food supply, the period of egg 
deposition of the radicicoles averages 45 days and may reach a 
maximum of 110 days. This average is nearly constant throughout 
the season. The average number of eggs deposited is about 117, 
but under certain conditions the number may be increased to 486. 
The daily average number is about 2J+ eggs, and as many as 23 
eggs have been deposited in 24 hours by a single phylloxera. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 33 

The rate of egg deposition is usually indicated by a sharp rise shortly 
after commencement, followed by a gradual decline. During the 
period of egg laying the adult feeds, and after the last egg is laid 
may live for as long as three weeks. 

Incubation naturally is influenced by temperature, and the dura- 
tion of the incubation period may vary from five days in July to 
over a month in December. Very few eggs are laid in December, but 
in March and April, when many eggs are deposited, the maximum 
period of incubation is 27 days. 

The larvae mature in midsummer in about 15 days, and in April 
and November in about 34 days, and the hibernant generation de- 
velops in about 180 days. The winged forms mature more slowly 
than do the wingless individuals, since the fourth or nymphal instar 
is noticeably extended beyond that of the corresponding wingless 
stage. 

In the late fall a few individuals intermediate in structure be- 
tween the nymphs and radicicoles are found. These are called 
" nymphicals " or intermediates and, so far as is known, they de- 
posit the same type of eggs as the radicicoles, although they are 
not prolific. From egg deposition to the molting of the final skin, 
the period covered by the sexes, which develop from eggs of two 
sizes laid by the winged forms, was about 12 days in confinement. 

All stages of the phylloxera molt four times, and the first instar 
is always the longest (the adult instar excepted) . 

HIBERNATION. 

The phenomenon of hibernation. — Throughout autumn and early 
winter an ever-increasing percentage of newly hatched radicicole lar- 
vae, instead of increasing in size and maturing normally, remain 
as very small brown phylloxera? (PL IX, d, p. 64). As winter pro- 
gresses, the mature individuals die, leaving only the small brown 
larvae and a few unhatched eggs. As soon as these late eggs hatch, 
the larvae settle down, becoming brown like the others. These small 
larvae are the hibernants, and as such they remain throughout the 
dormant period. Occasionally phylloxerae that have passed one or 
two molts hibernate. This type is quite unusual, and probably con- 
sists of individuals that have reached a certain stage of development 
and are unable, through lack of nourishment, to mature, most of them 
dying before spring. 

Hibernant larvae occur on all kinds of vines — on viniferae and 

on American varieties and hybrids. While this form of phylloxera 

occurs more or less sparingly on American resistant vines (Vitis 

riparia, V. rupestris, V. berlandieri, etc.) and on some American 

1900°— 21 3 



34 BULLETIN C03, U. S. DEPARTMENT OF AGRICULTURE. 

nonresistant X resistant hybrids, it finds its greatest development 
on vinifera? and on certain American nonresistant varieties of Vitis 
labrusca, V. aestivalis, and V. monticola. On the wild species of 
Vitis of the eastern and southern parts of North America, consid- 
ered as the original hosts of the grape phylloxera, is found a com- 
plicated life C3^cle embracing gallicoles (gall lice), radicicoles (root 
lice), winged migrants, sexed forms, winter eggs, and true stem 
mothers. The hibernants are rarely abundant on these wild spe- 
cies of vines, and the winter is passed chiefly in the winter-egg 
stage. On vinifera (Vitis vinifera) this complicated life cycle is 
rarely completed, and a simpler one, comprising only the root forms, 
obtains. Therefore, in the absence of the Avinter egg, the winter 
period must be tided over by another form, which is supplied in 
the hibernant larva. It appears that, to the phylloxera, Vitis vinifera 
is an acquired food plant, and that the nature and construction of 
the Old World grapeAdne has changed the habits and life history 
of the grape phylloxera feeding on it. 

On vinifera?, although hibernation takes place chiefly on the 
larger roots and on the subterranean portion of the trunk, it occurs 
also on nodosities and on smaller roots. 

Hibernants are located both on lesions and on the normal surface 
of the roots. On the varieties of resistant vines and certain hybrids 
(vinifera X resistant and resistant X American nonresistant) that 
have been examined, it has been found that hibernation occurs 
chiefly on nodosities and less frequently on the normal root surface. 
Tuberosities rarely are formed on these vines. On American non- 
resistant and vinifera X nonresistant hybrids, hibernation was 
chiefly of the type found on the vinifera?. On Golden Champion, 
Agawam, Catawba, Isabella, Lenoir, and Delaware, hibernants oc- 
curred on tuberosities, nodosities, and the normal root surface. On 
Moore's Early they were located on nodosities and on larger roots 
but not on tuberosities. 

Appearance of hibernants. — The hibernants (PL IX, d, e, f, 
p. 64) appear as little oval brown insects flatly appressed to the 
surface of the root, their legs folded underneath the body. The 
antenna? are borne at right angles to the major body axis, and hardly 
project beyond the maximum width of the body. The whole insect 
generally shows one color, but sometimes there is a darker median 
longitudinal line, except on the head. In those individuals which 
have molted before going into hibernation, a similar shade of darker 
brown occurs. Occasionally lighter individuals will be noted, but 
none is ever as pale as the growing and feeding radicicole larvae. 
Hibernants located under several layers of bark, as a rule, exhibit a 
paler color than those living more exposed. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



35 



FIXATION OF BEAK. 



To secure information regarding the fixation of the beak in the 
root five lots of hibernants were examined on January 23, 1914. 
The results are given below. 

Table II. — Fixation of beak of hibernants of the grape phylloxera. 



Lot No. 


Number 
of indi- 
viduals. 


Number 
with 
beaks 
fixed. 


Number 
with 
beaks 
free. 


Remarks. 


1 


25 
25 

25 
25 
20 


12 
24 

16 
22 

8 


13 
1 

9 
3 

12 


Under 2 layers of bark on large root. 


2 


Large root; insects originally under 2 layers of bark, 


3 


but layers peeled off some time before experiment. 
Small root; insects on tuberosities. 


4 


Do. 


5 


"Under several layers of bark on stock of vine 3 inches 




below soil surface. 


Total 


, 120 


82 


38 





In lots 1, 2, and 5 the individuals that had their beaks fixed in the 
roots were obviously the more healthy. In lots 3 and 4 all the 
phylloxeras appeared equally healthy. They were on more succulent 
roots than those in lots 1, 2, and 5, and it may be that on such succu- 
lent food the hibernants have a habit of driving in and drawing out 
their beaks at will, whereas on harder roots this would not be pos- 
sible. It is evident that hibernants situated on the outside bark of a 
root are likely to be washed off by water if their beaks are not in- 
serted into the root. The experiment would serve to indicate that in 
the individuals of lots 1 and 5, wherein the hibernants were protected 
under layers of bark, the majority had their beaks free, while in lots 
2, 3, and 4, wherein the hibernants were exposed, the majority had 
their beaks inserted, so that it appears that the fixation of the beak 
acts as an anchorage. 



NOURISHMENT. 



The hibernant larva partakes of nourishment very slightly, if at 
all, before it settles for the winter. During the period of true 
hibernation it apparently takes no nourishment. Therefore it is 
probable that the great majority of the hibernants take their first 
food when they arouse themselves from their lethargy in spring. Of 
those observed to feed before hibernating, a few pass one or rarely 
two molts, while the rest remain unmolted but larger in size than the 
true hibernating larva. The writers have observed instances in 
which severed pieces of roots infested by hibernants formed winter 
lesions, the presence of the beaks in the root affording a stimulus. 



36 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

Hibernants on nodosities sometimes keep these fresh until spring 
by the stimulating action of their implanted beaks. Such nodosities, 
especially in vinifera and labrusca vines, otherwise usually fail to 
pass the winter in a fresh condition, as they are susceptible to rot 
through moisture. 

DURATION OF IN STAR. 

With the exception of the winter egg, the hibernant instar is the 
longest found in the life cycle of the phylloxera. A series of experi- 
ments undertaken in the laboratory during the winter 1911-12 showed 
that the average for 12 individuals was 183 days, or approximately 
half a year. A later series of experiments, which took place both 
on living vines and in the cellar on severed roots, indicated that 
this period may be shortened to four and one-half months and length- 
ened to seven and one-half months, dependent, as usual, on food, 
temperature, and moisture conditions, and that six months is about 
the average period for the development of the hibernants. This 
period was considered from the date in the fall on which the insect 
hatched from the egg to that on which the insect became mature the 
spring following. The actual state of dormancy is from three to six 
weeks shorter, and thus approximates five months. Granted that 
radicicoles may live for three months after reaching maturity, it 
is apparent that hibernating phylloxeras might attain a total longev- 
ity of over 10 months. 

MOVEMENT ON THE ROOTS. 

On a sound root, the overwintered phylloxerse rarely change their 
positions while they develop. If situated on tuberosities or nodosi- 
ties, they cause these lesions to become enlarged, and if situated on 
the normal root surface they cause the formation of new lesions. 
Occasionally they develop without causing a lesion to appear. On 
decayed and decaying roots, they move away after the first or later 
molts and seek better food. This movement is both upward and 
downward, indiscriminately, and is never extensive. The individ- 
uals show only feeble inclination toward migration. This genera- 
tion appears to be the lowest in vitality and the quickest to succumb 
to adverse conditions. 

GROWTH AND MATURING OF THE HIBERNANTS. 

During the true hibernation period the phylloxerae apparently 
take no food, and if any be taken no increase in growth can be noted. 
Later a slow but appreciable growth may be observed, which indi- 
cates the termination of the true hibernation period. A growing 



THE GKAPE PHYLLOXERA IN CALIEOPvNIA. 37 

period, varying from one to six weeks, ensues, and after this the first 
molt occurs. In the course of from two to six weeks after the first 
molt three additional molts take place, and at the conclusion of the 
fourth molt the phylloxera is mature. This spring growth and de- 
velopment, as observed in the vineyard and in cages, is extended over 
a period of about three and a half months, and usually occurs during 
the period from February 15 to April 15. The commencement of 
growth in phylloxera is noted to be coincident with the first move- 
ment of sap in the vine, and naturally both are influenced by pre- 
vailing meteorological conditions. Upon reaching the adult stage 
the hibernant immediately begins the deposition of its eggs, and in 
this manner the series of parthenogenetic generations destined to 
continue through the season is commenced. 

Measurements. — During the winter of 1913-14 hibernated larvae 
were measured at certain intervals to determine at what time the 
spring growth started. On October 27, 1913, seven individuals 
which had recently hibernated averaged 0.333 mm. in length and 
0.202 mm. in maximum width ; on January 6, 1914, four individuals 
which had hibernated in October, 1913, averaged 0.337 mm. in length 
and 0.198 mm. in maximum width; on February 23, 1914, four indi- 
viduals averaged 0.410 mm. in length and 0.217 mm. in maximum 
width; and on March 10, 1914, five individuals averaged 0.421 mm. 
and 0.241 mm., respectively. Between October and January there 
was no difference in size, but between January 6 and February 23 
there was a marked difference, both individually and collectively, 
showing that between these dates the hibernants had begun to feed, 
The measurements of the individuals taken on March 10 showed 
that considerable growth occurred between February 23 and that 
date. None of the insects measured had molted, and observations 
showed that perceptible growth did not begin before February 10. 
The average length of the beak of the newly hatched radicicole 
destined to hibernate is slightly over 0.2 mm., but after it has been 
inserted in the root it becomes somewhat telescoped and measures 
about 0.17 mm. 

The majority of the hibernants before they start to grow are 
smaller than the newly hatched radicicoles, and therefore they actu- 
ally shrink in size after they hatch from the egg and settle to 
hibernate. Those that feed before hibernating do not shrink to 
such a small size. 

Hibernation in vineyards. — In the vineyards it has been observed 
that the phylloxeras enter into hibernation as early as September 15 
and as late as December 15. Prior to October 1 only a small per- 
centage of hibernants have been found, and after November 20 



38 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

only a small percentage have been observed that were not hibernants. 
The greater number of the aphids enter hibernation during October 
and the first half of November; that is, a majority of the larvae 
hatching from eggs in this period settle down to hibernate. A few 
of those hatching before October become hibernants. After Decem- 
ber 1 it is very unusual to find eggs. The phylloxeras do not enter 
into hibernation all at one time, and even on a single given grape- 
vine the entering into hibernation is protracted over several weeks 
and often as long as two months. The causes that induce the young 
larvae to hibernate instead of proceeding with their normal growth 
are three: (1) Condition of sap flow, (2) condition of food, (3) 
temperature and humidity. Hibernation in general takes place at 
the time when aerial and radical growth of the vine slacken in the 
fall. If the soil temperature is high, there is a tendency to post- 
pone hibernating until some time after the terminal growths have 
apparently ceased. On decayed and decaying roots the phylloxeras 
hibernate earlier and on nodosities and sound tuberosities later than 
on the surface of a normal root. Kegarding the influence of tem- 
perature, Mayet (15), in discussing the hibernant form, states that 
eggs die when the temperature falls below 10° C. He states further : 

This temperature of 10" C. appears to be the minimum under which the in- 
sects become numb, and above which they go out of their torpor * * * M. 
Maurice Girard proved, experimentally, by means of a freezing mixture, that 
the phylloxera would sustain a temperature of — 8° and — 10° C. without dying. 

The present writers' observations in the vineyards show that, 
broadly speaking, when the temperature drops to a minimum of 66° 
F. about half the individuals are hibernants, and when the maximum 
in spring has risen to 58° F. about half the individuals have com- 
menced growing. The phylloxeras enter hibernation under a consid- 
erably higher temperature than that which obtains at the time their 
spring growth begins. 

Character of soil has no direct influence on hibernation, but it may 
have an indirect influence in so far as it may affect the condition of 
the roots. The heavier soils hold the moisture longer than those 
of lighter types, bringing about a more rapid decay of the roots and 
compelling early hibernation. Cold soils also force the insects into 
early hibernation. 

In the vineyards the bulk of the hibernants occur on the lower 
part of the stump and on the basal portions of the main roots. Hiber- 
nants also ascend older vines several inches above the soil surface, 
where they are concealed under layers of bark. Often most of those 
that go above the soil surface perish from cold (16). On the smaller 
rootlets are found small numbers of hibernants, many of them on 
nodosities on which they pass the winter, frequently with a consid- 
erable percentage of mortality. On vines that have been heavily 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 39 

attacked for years previous, it is unusual to find hibernants, except 
at the base of large roots or on the trunk, because the roots that were 
attacked the previous summer tend to rot badly when moistened by 
winter rains, and consequently most of the hibernants remaining 
thereon die, and only those higher up on sounder pieces of roots 
survive in abundance. The basal part of a large root is not gener- 
ally ' badly attacked during summer, and so there are not enough 
tuberosities to rot it during the succeeding winter. 

A very noticeable tendency is for the hibernants to congregate in 
masses. Such masses occur on the normal surface of the root, on 
tuberosities, on nodosities, and under one or more layers of bark. 
Perhaps in general on a grossly infested vine more masses occur 
on the outside bark, but this is only because the preferred sheltered 
places are too few and are inadequate to cover all the phylloxera?. 
On younger vines a favorable location for hibernating is at the 
foot of the stump. On older vines this position is not so generally 
chosen. On vines which are only lightly infested the phylloxera? 
often congregate at certain spots, while other spots, apparently as 
favorable, are neglected. On the heavily infested vines all the favor- 
able spots for hibernation are utilized, the majority of the insects 
being forced to locate on the unsheltered outside bark of the root. 

In vineyards the growth and maturing of the hibernants in spring 
extends over a period about as long as that covered by the entering 
into hibernation in the fall. The growth first becomes apparent 
about February 25, and proceeds until the time arrives when the 
most tardy individuals mature. Immature hibernants are found as 
late as May, but by April 15 the great majority have become mature. 
Just as in the case of " entering hibernation," so in the " spring 
development," a wide range occurs even on single given vines. The 
earliest individual may commence growth two months or more 
before the most tardy. On an average, it takes about five weeks 
for the hibernants to mature after they have first shown perceptible 
growth. On sound lesions this is shortened to as much as three 
weeks, and on decaying portions of roots lengthened to as much as 
eight weeks. Many of those on decayed roots die from ill nour- 
ishment before maturing, but the majority of such move away to seek 
better food. 

The forces which influence the growth of the phylloxera? in spring 
are a reversal of those which impel hibernation in the fall. As 
stated, the phylloxera? start to grow about the time when the sap 
begins to flow. On dying vines in which the sap flow is either not 
apparent or very weak, the phylloxera? on the more healthy roots 
show perceptible growth in like manner to those living on healthy 
vines, in which case their activity is supposedly due solely or chiefly 
to meteorological effect. - The spring growth on unhealthy roots 



40 BULLETIN 903, IT. S. DEPARTMENT OF AGRICULTURE. 

is curtailed and commences late. On nodosities and tuberosities 
which have remained fresh during winter, the succulent condition of 
the food induces early growth on the part of the phylloxeras. 

Hibernation under cellar conditions. — During the period 1911-1915 
hibernation was observed on severed roots in the laboratory cellar. 
These roots were kept in glass battery jars and in petri dishes and 
remained in a fresh condition when systematically moistened. Good 
callus growth and sometimes fleshy offshoots were obtained, es- 
pecially when a layer of moist sand was placed in the bottom of the 
dishes. The phylloxeras caused the formation of lesions in similar 
manner as on roots of living vines. 

Under cellar conditions hibernation was often prolonged beyond 
the period found to occur in the vineyards, and this prolongation re- 
sulted in a small number of phylloxeras maturing very late. The 
" awakening " period in spring was not different from that found 
in the vineyards under equalized temperatures. Under cellar con- 
ditions a greater mortality existed among hibernants than in the 
vineyards. This was supposedly due to the greater range of daily 
temperatures, to the abnormal condition of the roots severed from 
the vine, and to the apparent lack of sap flow. In the cellar hiber- 
nants a greater variation in size and color existed, even in unmolted 
phylloxeras, than in the vineyard on living vines. A very small per- 
centage of hibernants were observed to pass the winter in the second 
and third instars. Eggs were never observed to pass the winter, 
since all eggs laid late in the year hatched in due course according to 
temperatures. No mature or f ourth-instar phylloxeras were observed 
to hibernate. Adult radicicoles in late autumn, as at other times, 
lived for some days or even weeks after they deposited their last egg, 
but none was found that survived until spring. 

Observations on the hibernation of phylloxeras reared on sev- 
ered roots under cellar conditions may be summed up as follows: 
The first phylloxeras entered hibernation as early as August, in ex- 
treme cases in July, and the percentage of hibernating individuals 
from that time gradually increased. By October 1, it was found 
that on the average about 30 per cent of the individuals were hiber- 
nants. By the last of October from 85 to 90 per cent were hibernants. 
All the living phylloxeras, however, were not hibernants until the end 
of December, and during November and December a dwindling num- 
ber of adults and unhatched eggs were observed. All larvas hatching 
after November 1 settled down to hibernate, and about three-fourths 
of those which hatched in October did likewise, the individuals com- 
prising the other fourth maturing toward the end of October and 
in November and continuing to deposit eggs up to December. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 41 

The spring growth began in the earliest individuals about Jan- 
uary 25 ; by the middle of March nearly all the phylloxera? were 
growing and about half were mature. Some individuals remained 
dormant as late as the middle of April, and the most tardy did not 
mature until the middle of May or even later. On very poor 
roots many never matured at all. The period of appreciable growth 
prior to the shedding of the first skin averaged two weeks and the 
period from first molt to maturity about three weeks. On vigorous 
roots the hibernants mostly developed without changing their posi- 
tions, but they forsook in large numbers roots decayed or decaying. 
These emigrations occur both before and after molting but chiefly 
just following a molt. 

In comparing the hibernation on severed roots as observed under 
cellar conditions with that on living roots as observed in the vine- 
yards, in pots, and in special box cages, several points are to be noted. 
(1) The phylloxera? on the severed roots in the cellar entered hiber- 
nation in a more irregular manner than did those on the living vines. 
This condition appears due to the following causes : The severed roots 
were cut off from a normal flow of sap, the temperature fluctuations 
in the cellar were greater, and in the months of July, August, and 
September the temperature reached a lower daily minimum than 
in the vineyards; (2) the phylloxera? hibernating in the cellar ma- 
tured earlier in the spring than those on living vines out of doors by 
reason of the higher temperature obtaining in the cellar during 
January and February; (3) there was a greater mortality among the 
hibernants in the cellar, due to the fact that the severed roots often 
dried up or decayed before spring; (4) numbers of the phylloxera? 
occasionally hibernated after they had shown appreciable growth 
or even cast a skin. This phenomenon rarely has been observed 
on living roots. In other respects the behavior of the phylloxera? 
on severed roots did not differ from that on living roots. In excep- 
tional cases vigorous pieces of severed roots were observed to send 
out fleshy rootlets in early spring, indicating a modified sap flow, 
and on such roots the phylloxera? moved early and appeared to 
be influenced by this flow of sap. The comparatively high winter 
temperatures obtaining in the cellar undoubtedly produced this modi- 
fied sap flow, since it occurred much earlier than the corresponding 
flow in the vineyards. 

Hibernation on vinifera vines in cages, 1913-1 If.. — The following 
observations were conducted upon the roots of living vines of differ- 
ent varieties growing in special cages (Pis. V-VII, p. 52). The vines 
were young and satisfactory specimens for the experiments. The 
exposed portions of the roots between the upper and lower pots were 
about 4 inches long, one- fourth inch in diameter, and from 10 to 14 
inches below the soil surface of the upper pot. Although both ends 



42 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

of the exposed portions of roots were surrounded by an inch of fine 
sand, and all inoculations were made on these exposed portions, it 
frequently happened that phylloxera? found their way to the unex- 
posed portions, so that in the winter following the inoculations 
hibernants were found in both the exposed and unexposed portions. 

The temperatures in the cages differed but slightly from those re- 
corded simultaneously 2 feet below the soil surface in the laboratory 
vineyard. In 1913-14 in midwinter, however, the former touched a 
mark about 10° F. lower, besides being uniformly lower throughout 
December and January in both the seasons 1913-14 and 1914^-15. 
During the period (August to November) in which the phylloxeras 
entered hibernation there was no appreciable difference, and before 
the commencement of the spring growth of the hibernants the tem- 
peratures were again equalized. Thus, in the periods of entering 
into and awakening from hibernation, vineyard conditions were 
reproduced in the cages as far as temperature was concerned. Con- 
temporaneous vineyard observations show that the behavior of the 
hibernants on living vines in the cages simulated closely the be- 
havior of those in the vineyards in the locality, and the habit of 
clustering was often noted. The aphids entered into hibernation 
and showed spring activity much as they did in the vineyards, but 
in each phenomenon there was an exception. In 1914, six aphids 
out of a lot of nine individuals hatching between August 24 and 26 
proceeded to hibernate. Such early hibernation with succulent food 
present is quite unusual in the field. Again, in 1914, on another vine, 
part of a series of hibernants cast their skins as early as February 
23, indicating that growth commenced not later than February 15. 
In the vineyard, even upon warm soils, the first date of activity was 
never earlier than February 25. This early spring activity in the 
cages was possibly due to comparatively high temperatures in Feb- 
ruary, this being the only month during which the cage temperatures 
exceeded those in the soil. 

Hibernation on American resistant and nonresistant vines in cages, 
1914-15. — Along with the vinifera vines planted in the special cages 
for observing the phylloxera? on living roots, a number of American 
resistant and nonresistant vines were used for similar observation. 
The nonresistant varieties (propagated from Vitis labrusca and V. 
aestivalis) were Catawba, Isabella, Lenoir, Delaware, and Champion. 
The Muscadine (F. rotundlfolla) was used also. The resistant 
hybrids, some of which were grafted to vinifera?, comprised Mour- 
vedre X Rupestris 1202, Solonis X Riparia 1616, Berlandieri X Ripa- 
ria 157.11, Riparia X Rupestris X Aestivalis X Monticola 554.5, 
Aramon Rupestris Ganzin 1, Riparia Gloire de Montpelier, Rupes- 
tris St. George. These vines were planted in the spring of 1914 and 
inoculated thereafter. 



THE GEAPE PHYLLOXERA IN CALIFORNIA. 43 

On the Muscadine the phylloxera? upon hatching from the eggs 
refused to settle or feed. The nonresistant varieties were infested 
throughout summer and autumn, and on their roots the phylloxera? 
entered into hibernation from September 20 to the beginning of No- 
vember; in the case of the Champion, they hibernated as late as 
December 1. On the Catawba and Champion, the most heavily in- 
fested, the aphids began hibernation earlier; on the less infested 
Delaware, Isabella, and Lenoir, somewhat later. 

Aphids became active about the middle of February, and all 
hibernants were adult by April 13. This spring activity was some- 
what in advance of that occurring in vineyards, but was similar to 
that which occurred on the caged vinifera vines. On all nonresist- 
ant varieties it was observed that the hibernants massed on tuberosi- 
ties, nodosities, and the normal surface of the roots; and in cracks in 
a manner similar to that observed to occur on vinifera vines. 

On the resistant hybrids repeated inoculations during summer 
and autumn failed to produce more than an extremely light in- 
festation. The phylloxera? settled to hibernate during October, and 
at the end of that month all were hibernants. They were situated 
on side rootlets and on the normal surface of the root, but on the 
Rupestris St. George hibernants occurred also on nodosities which 
they had caused to form shortly after they settled. 

Hibernation on American vines in pots, 1912-1915. — A large series 
of 2-year-old vines (from cuttings) planted in 6-inch pots, originally 
used in resistance experiments and comprising resistant vines, we r e 
examined during the years 1912 and 1913 for hibernant observations. 
It was found that hibernation took place during the last half of 
October and first half of November and that the spring awakening 
proceeded from about March 10 to April 15. These vines were 
planted in light sandy soil. The hibernants settled chiefly on nodosi- 
ties and to a smaller extent on the surface of the larger rootlets. In 
the spring there was a great variation in the growth of the vines. In 
the majority of instances the phylloxera? on the early leafing vines 
molted sooner than those on the more backward plants. No tempera- 
ture records were kept with this series, but it is probable that the 
records taken 2 feet below the soil surface (Table XII) approxi- 
mated that which occurred in the pots in the winter of 1913-14. 

A further series (1914) of rooted vines in 9-inch pots, comprising 
Agawam, Isabella, Lenoir, Delaware, Catawba, and Champion, 
showed that with the exception of the Delaware, which was lightly 
infested, hibernation proceeded from about October 1 to November 
1, nearly all the insects being hibernants on the latter date. On the 
Delaware none of the phylloxerse were hibernants on October 30, 
and the roots were on that date still running strongly in sap, while 
the sap flow in the other varieties was weaker. The temperature in 



44 



BULLETIN 903, IT. S. DEPARTMENT OF AGRICULTURE. 



these pots was about the same as that occurring 2 feet below the soil 
surface. In the spring of 1915, on the Champion, Lenoir, Catawba, 
and Isabella, the phylloxeras began to grow about March 1. On the 
first three the bulk of the hibernants were mature April 6, but on 
the Isabella, which was moribund, more than half were unmolted. 
This vine was not retained further, but, considering the condition 
of its roots, it is not probable that any of the phylloxeras would 
have matured. The vine was too weak to send out new rootlets, and 
the roots showed much decay. The abundance of phylloxeras the 
summer previous had doubtless caused this weakness. 

THE RADICICOLE. 

EGG DEPOSITION. 

The adult radicicole commences to deposit eggs within 48 hours 
after the final molt. Occasionally there occur abnormal individuals 
which delay deposition of eggs as much as two weeks, and again 
there are others which fail to deposit eggs but continue alive for 
some weeks. 

Egg deposition on severed roots.- — Table III gives the summarized 
record of the egg deposition of radicicoles under cellar conditions 
during the years 1911-12. 

Table III. — Summarized record of egg deposition of radicicoles of the grape 
phylloxera under cellar conditions during 1911-12, Walnut Greek, Calif. 



Gener- 
ation. 



i 
1 
2 
3 
4 
'5-10 



Num- 
ber of 
adults. 



52 
45 
57 
17 
11 
27 



Egg-laying period for gener- 
ation. 



Apr. 21 to Oct. 1 

May 27 to Sept. 23 

June 29 to Nov. 6 

Aug. 4 to Dec. 7 

Sept. 5 to May 15, 1912. 
Apr. 26 to Oct. 6 



Number of eggs per 


Days 


in' period of 




adult. 




deposition. 


Maxi- 


Mini- 


Aver- 


Maxi- 


Mini- 


Aver- 


mum. 


mum. 


age. 


mum. 


mum. 


age. 


347 


4 


84.6 


110 


2 


55. 3 


486 


10 


192.0 


96 


5 


46.3 


287 


2 


102.0 


106 


1 


48.5 


266 


3 


141.8 


96 


2 


44 


119 


31 


67.2 


83 


23 


41.7 


137 


4 


35.5 


47 


3 


21.5 



Aver- 
age 
num- 
ber of 
eggs 
per 
adult 
per 
day. 



1.53 

4.1 

2.1 

3.2 

1.6 

1.7 



1 Overwintered generation. 2 Including 3 individuals which matured in 1912. 3 Throughout 1912. 

Neglecting the series of generations 5 to 10, the individuals of which 
suffered through abnormal food and other conditions, it is shown in 
Table III that the aphids of the second generation were the most 
prolific. One aphid deposited 486 eggs in 79 days, an average of 6.3 
per diem. The greatest number of eggs laid within 24 hours by a 
single adult was 23 and the longest laying period covered 110 days. A 
true seasonal average of the number of eggs deposited by each aphid 
was 117 for 1911 and a similar average of the number of eggs per 
diem per aphid about 2£. 



THE GKAPE PHYLLOXERA IN CALIFORNIA. 45 

In 1913, between June 26 and November 14, a series of observations 
on fecundity under adverse food conditions was made. Among a 
large number of aphids, on two occasions only were as many as six 
eggs deposited in one day by a single individual. In the cellar, 431 
eggs were deposited in a total of 331 days (1.3 eggs per diem per 
aphid), and in an electric incubator, wherein a slightly higher 
temperature was maintained, 787 eggs were laid in a total of 463 days 
(1.7 eggs per diem per aphid). These averages were considerably 
less than corresponding ones found to result in the 1911 series, yet the 
insects raised in the incubator were subjected to higher temperatures 
than were those in 1911, raised in the cellar. 

Egg deposition on living vines. — During the years 1913, 1914, and 
1915, series of generations were raised on living vines in cages. These 
vines were all vinif erse, and comprised the following varieties : 
Muscat, Zinfandel, Mission, Burger, Thompson's Seedless, and Gren- 
ache. The principal object in this work was to check up on the 
previous 2-year study of root cuttings under cellar conditions. The 
initial inoculations in 1913 were made with eggs laid by adults of the 
overwintered generation on Zinfandel vines in the vineyard, and thus 
no record of the egg production of the overwintered adults was 
secured in the cages. Of the first generation, records of 10 indi- 
viduals were taken, but a complete record of only one was made, and 
this adult, between June 25 and July 14 (20 days) , deposited 121 eggs, 
the largest number in a single day being 12. The 10 adults deposited 
482 eggs in 95 days, or an average of 3.1 eggs per diem per adult. 

Most of the individuals died early, and it is assumed that if they 
had been allowed to lay their full complement of eggs, the period 
of decline would have reduced this average. These adults were pro- 
duced, 7 on Burger roots and 3 on Mission roots. It appeared that 
those on the Mission were the more prolific. On both varieties 
some were situated on lesions they had caused to form. These aver- 
aged better in egg production than the others situated on the nor- 
mal root surface. Records for 14 adults of the second generation 
were taken. On a very healthy Mission root, living on lesions, 4 
adults averaged 4.5 eggs per adult per diem. On two less healthy 
Mission roots of the same cage vine, 6 averaged 2.4 eggs per adult 
per diem. On a very healthy Burger root 4 averaged 3.9. The 
longest egg-laying period for any adult of this generation was 26 
days and the maximum eggs per day 15. In all, 489 eggs were laid 
in 136 days, 3.6 eggs per adult per diem. 

The egg-laying period of this generation ran from July 8 to 
August 15, with an average temperature of 68° F. Four adults of 
the third generation deposited 284 eggs in 88 daj^s, at an average 
of 3.2 eggs per diem per adult; the longest egg-laying period was 
28 days and the maximum number of eggs per diem was 8. These 



46 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

adults lived on a healthy Muscat root on tuberosities, their egg- 
laying period being from August 28 to September 26, under an 
average temperature of 64° F. One of them did not commence de- 
positing eggs until the sixth day after it matured, having moved 
about considerably meanwhile. The fourth-generation phylloxeras 
wintered on the same root upon which their immediate progenitors 
had oviposited and matured in the spring of 1914. Of these, 3 
adults laid 79 eggs in 42 days (aggregated) or 1.9 eggs per diem per 
adult. The maximum number for one day for a single adult was 
4 and the longest egg-laying period 24 days. In this period one 
adult laid 56 eggs. The egg-laying period, toward the end of which 
the root became lightly decayed, ran from April 6 to May 8, under 
a temperature averaging 58° F. 

In the ensuing generations throughout 1914 and 1915, the egg- 
laying records were mostly incomplete. Records of the fifth gen- 
eration on Muscat in the period May 28 to June 11 show an average 
number of eggs per diem per adult to be 2.8, the largest number 
deposited in a single day by a single adult being 5. The average 
temperature was 65° F. Records of the seventh generation on a 
slightly decayed Grenache root, July 29 to August 8, show an av- 
erage number of eggs per diem per adult to be 5.4, and the maximum 
number of eggs laid in a single day to be 7. The temperature aver- 
aged 71° F. The records of these two lots are much too meager for 
comparisons. 

In comparing the egg production on the living vines with that on 
root cuttings, it should be stated that during the summer and fall 
months the aphids on the former enjoyed higher temperatures. This 
advantage was somewhat counterbalanced by the greater daily 
fluctuations in temperature which took place on caged living vines 
and which frequently resulted in a daily minimum lower than that 
simultaneously occurring in the laboratory cellar in which the root 
cuttings were kept. 

As a general rule the egg-depositing capacity of the adult in- 
creases rapidly after maturity, and after the zenith is reached de- 
creases slowly, so that half the complement of eggs is deposited 
before one-third of the egg-laying period is completed. 

The condition of the food is the chief factor in the production of 
eggs, but there is also a meteorological control. Frequent fluctuations 
in temperature and humidity adversely affect deposition. 

Extrusion of the egg. — During the process of egg extrusion, which 
occupies from 20 to 40 minutes, the abdomen of the adult radicicole is 
considerably distended. It is apparent, therefore, that when an 
adult deposits 23 eggs within one day, extrusion will be taking place 
intermittently for a very considerable part of the day. During the 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



47 



period of egg deposition, the aphids often change their orientation 
by pivoting about the beak. 

Time of day of oviposition. — Between April 28 and May 25, 1913, 
records were taken in the cellar to obtain data upon the time of day 
of oviposition. The maximum daily temperature occurred about 
6 p. m., 9 and the minimum about 7.30 a. m. Between 9 a. m. and 
5 p. m. (8 hours), 41 eggs were deposited, and between 5 p. m. and 
9 a. m. (16 hours), 52 eggs were deposited in the 27 days. Between 
9 a. m. and 5 p. m., there was an average hourly temperature in 
excess of that occurring between 5 p. m, and 9 a. m. of about 0.02° F. 
It is apparent that the higher temperature of the shorter period 
caused a comparatively greater number of eggs to be deposited, 
since the 52 eggs were laid in exactly double the time in which the 
41 were deposited. 

Egg fertility and mortality. — A large series of experiments took 
place in 1911 to determine the fertility and mortality percentages of 
the eggs of the radicicole phylloxera. These were carried on about 
evenly throughout the year. One series was conducted under cellar 
conditions in petri dishes, and the other took place in the laboratory 
under a higher temperature and was exposed to subdued daylight. 
Table IV gives the results of these experiments : 

Table IV. — Fertility and mortality of the radicicole egg of the grape phylloxera, 

Walnut Creek, Calif., 1911. 



Generation and environment. 


Total 
number of 

eggs 
deposited. 


Number of 

eggs 

hatched. 


Number of 
eggs tbat 

failed 
to hatch. 


Percentage 
hatched. 


Unknown (various) 


965 


772 


193 


80.00 






1 (Cellar) 


1,000 
490 


911 
422 


89 
68 


91.10 


1 (Exposed to ligbt) 


86.12 






1 (Total) 


1,490 


1,333 


157 


89.52 






2 (Cellar) 


1,840 
245 


1,716 
236 


124 
9 


93.26 


2 (Exposed to ligbt) 


96.33 






2 (Total) 


2,085 


1,952 


133 


93.62 






3 (Cellar) 


1,112 
524 


987 
486 


125 
38 


88.76 


4 (Exposed to ligbt) 


92.75 






Grand total 


6,176 


5,530 


646 


89.54 







There was no appreciable difference between the fertility of 
those reared in the cellar and of those reared in the higher tempera- 
tures of the laboratory rooms. The results indicate that on the aver- 
age almost 9 eggs out of every 10 laid will hatch. It is probable that 
vineyard conditions produced similar averages as no predators or 
other causes that might bring about a different average have been ob- 
served with the exception of the case of excessive spring moisture 
acting upon the eggs laid by the overwintered adults and in the case 

8 All references to clock time refer to " Standard time." 



48 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



of eggs laid on rotting tuberosities. The eggs have a considerable 
resistance to water at ordinary temperatures and may also hatch 
under water. Many, probably 25 per cent, of those that are laid on 
rotting tuberosities fail to hatch. They seem to be so impregnated 
with dampness and influenced by the rotting root tissues surrounding 
them that they turn dark brown prematurely and finally collapse 
after the embryo dies. It must be considered also that very slight 
pressure applied to the eggshell may rupture it and kill the em- 
bryo. 

INCUBATION PERIOD. 

The first incubation record at Walnut Creek took place during 
April, 1909. Between April 9 and April 26, 24 eggs were observed 
in the laboratory with the results shown in Table V : 

Table V. — Incubation period of the eggs of the grape phylloxera, Walnut 

Creek, Calif., 1909. 

Days. 

Average incubation stage 13. 8 

Maximum incubation stage 15 

Minimum incubation stage 12 

No temperature records were taken. The eggs were presumably 

deposited by overwintered adults. During 1911 and 1912 a large 

series of incubation records was obtained. Table VI gives incubation 

records for each generation during 1911. 

Table VI. — Incubation records of the egas of the grape phylloxera at Walnut 

Creek, Calif., 1911. 



Genera- 
tion. 


Environment. 


Dates of period of 
incubation. 


Average 
tempera- 
ture. 


Number 

of eggs 

laid. 


Incubation period. 


Maxi- 
mum. 


Mini- 
mum. 


Aver- 
age. 


1 1 


Cellar 


Apr.28-May 18 

June 4-Aug. 19 

June 13-Sept. 6 

June 13-Aug.l9... 

June5-Aug. 18 

July.7-Aug.20 
Aug. 9-Sept. 2 
Aug.18-0ct.26.... 


61 
64 
( 3 ) 

64.5 

00 
64.6 

( 3 ) - 
64 


49 
889 
412 

1,797 

235 

969 

551 

10 


Days. 

17 

15 
13 

14 
11 
14 

10 
18 


Days. 
10 

8 

7 

7 
6 
7 
6 
7 


Days. 
13.6 


21 


.do 


10.8 


21 
II 


Laboratory shelf. . . 
Cellar 


9.8 
10.2 


II 
III 


Laboratory shelf. . . 
Cellar 


8.5 
11.7 


IV 
IV 


Laboratory shelf. . . 
Cellar 


7.2 
13.3 









i Eggs deposited by overwintered adults. 

2 Later series of eggs deposited by overwintered adults. 

;1 Temperature at least 5° higher tban that in cellar at corresponding dates. 

From Table VI it will be seen that the influence of temperature 
was very considerable. The records of 1912 are much more scanty 
and bear out the observations of 1911. Under an average tempera- 
ture of 70° F. the egg stage in 1912 averaged 8.9 days, with a maxi- 
mum and minimum of 10 and 7 days, respectively. The period cov- 
ered was from June 19 to October 3, but the great majority of the 
total of 55 eggs were laid during June. A small series of 27 sixth- 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



49 



generation eggs, laid May 6 to 8, 1912, under an average temperature 
of 63° F., incubated in an average of 10.7 days. 

The results shown in Table VII were obtained during 1911 and 
are in part a complement of those shown in Table VI : 

Table VII. — Incubation records of the eggs of the grape phylloxera, Walnut 

Creek, Calif., 1911. 



Group 

No. 


Environment. 


Average 
tempera- 
ture. 


Month of 
incubation. 


Number 
of eggs. 


Egg stage. 


Average. 


Maxi- 
mum. 


Mini- 
mum. 


1 


Exposed to light 


57 
60 
65 
52 

62 


May 


43 

177 

• 352 

16 
323 


15.14 
11.03 
9.07 
15.09 
10.66 


18 
15 
12 

18 
14 


13 


2 


do 


g 


3 


do 


June 

November . . 
May- June... 


8 


4 


do 


15 


5 


In darkness, laboratory drawer. . . 


9 



The eggs of the first four groups in the preceding table were 
exposed to light on a shelf in the laboratory, and those of group 5 
were incubated in a drawer in the laboratory. Both lots were sub- 
jected to a very abnormal fluctuation of temperature, this fluctuation 
in some cases reaching 20° F. daily. 

In 1912, 1913, and 1915 some additional incubation records were 
obtained, and Table VIII indicates the relations between tempera- 
ture, environment, and incubation to cover the four years, 1911, 1912, 
1913, and 1915. 

Table VIII. — Relation between incubation, ^temperature, and environment in the 
egg deposition of the grape phylloxera, Walnut Creek, Calif., 1911-1913 and 
1915. 



Lot 
No. 


Year. 


Number 
of eggs. 


Average 
daily 

tempera- 
ture. 


Incuba- 
tion. 


Remarks on environment. 


1 


1911 


16 

13 

26 

43 

17 

177 

16 

49 

38 

26 

48 

28 

889 

10 

1,797 

969 

286 

352 

13 

20 

22 

22 

62 

21 

55 

61 

38 


• °F. 
52 
55 
56.6 
57 
59 
60 
60.5 
61 

61.3 
63 
63 
63.8 
64 
64 
64.5 
64.6 
65 
65 
65 
67 
67.3 
68 
68 
68.5 
70 
70.3 
72 


Days. 

15.09 

20.50 

1 19. 60 

15.14 

15.50 

11.03 

15.40 

13.60 

15.50 

10.70 

15.50 

11.00 

10.80 

13.30 

10.20 

11.70 

10.29 

9.07 

9.40 

9.65 

8.80 

9.00 

2 7.00 

7.60 

8.90 

8.40 

8.70 


Exposed to light. 


2 


1915 


Cellar. 


3 


1913 


Do. 


4 


1911 


Exposed to light. 
Cellar. 


5 


1915 


6 


1911 


Exposed to light 
Cellar. 


7 


1915 


8 


1911 


Do. 


9 


1913 


Do. 


10 


1912 


Do. 


11 


1913 


Do. 


12 


1915 


Do. 


13 


1911 


Do. 


14 


1911 


Do. 


15 


1911 


Do. 


16 


1911 


Do. 


17 


1911 


Laboratory drawer — darkness. 


18 


1911 


Exposed to light. 
Cellar. 


19 


1915 


20 


1913 


Do. 


21 


1915 


Do. 


22 


1913 


Do. 


23 


1915 


Do. 


24 


1915 


Do. 


25 


1912 


Incubator. 


26 


1913 


Do. 


27 


1913 


Do. 









1 Maximum, 27 days. 
1900°— 21 4 



2 Minimum, 5 days. 



50 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

Examination of Table VIII shows that the incubation period 
gradually becomes shorter as the temperature rises. 

The exposure to light apparently produced abnormal rapidity 
in the development of the eggs. In lot 18 this influence was scarcely 
felt, while in lots 1, 4, and 6 it was very cogent, and it is evident that 
exposure to light is chiefly influential under low temperatures. The 
comparatively slow development of lots 25 to 27 apparently can be 
laid only to temperature fluctuations obtaining in the incubator. 
This fluctuation in the incubator sometimes consisted in the mainte- 
nance of a lower minimum for a longer period than that which 
obtained in the main part of the cellar. Such temperatures possibly 
would exert a retarding effect upon egg development that would 
not appear in the averaged readings of the thermometer. 

Even among the lots kept in the cellar under similar conditions 
there were apparent exceptions to the rule that "the higher the 
temperature the shorter the period of incubation." One such instance 
is that of lots 15 and 16, in which two large series were used, yet 
under temperatures differing but 0.1° F. there was a difference in the 
average incubation periods of one and a half days. 

Among the individuals enumerated in Table VIII the maximum 
egg stage was 27 and the minimum 5 days. The respective average 
temperatures influencing the two individuals were 55° F. and 68° F., 
and both were incubated in the cellar. It was possible only to estimate 
an annual average incubation stage, and this was about 11 days. 
It should be added that eggs have been observed in December to 
incubate in a period exceeding 30 days, but it is unusual to find eggs 
at this time of year. 

Experiments conducted in the cellar demonstrated that eggs in- 
cubated as rapidly in arid as in humid surroundings, but submergence 
in water lengthened the incubation period, even under equal tem- 
peratures. 

Incubation on living roots. — During the years 1913, 1914, and 
1915 biologic records were made on the living roots of young vines 
of viniferae and vinifera X American hybrids. A series of gen- 
erations were conducted during these three years, and incubation 
was observed for each generation. In most cases immediately after 
deposition the eggs were removed to an unifested root, but in some 
they were allowed to incubate where they had been deposited. The 
cages containing the experimental vines were all placed together in 
one trench, and the temperature was alike in -all of them. Table 
IX indicates the incubation periods with reference to temperatures 
and time of year. The years are not given, as in some instances 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



51 



single lots containing individuals incubating under the same average 
temperatures but belonging to more than one year have been com- 
bined. 

Table IX. — Incubation of the eggs of the grape phylloxera on living roots, 

Walnut Creek, Calif., 1913-1915. 



Lot number. 


Number 
of eggs. 


Average 
tempera- 
ture. 


Incuba- 
tion. 


Months or month. 


1 


19 
11 
11 

7 
6 
( 2 ) 
28 

( 2 ) 

3 
11 
23 
26 
21 
11 
45 
23 

8 


o F 

56.8 

57 

58 

58.5 

60 

61.8 

62 

63 

64 

66 

68 

69 

70.5 

71.5 

72 

72.5 

73 

73.2 


Days. 

119.0 

15.1 

14.8 

15.0 

12.3 

11.2 

9.0 

9.0 

9.7 

3 9.5 

10.5 

3 8.2 

3 7.7 

9.4 

8.4 

3 7.7 

3 7.0 

36.4 


March to April. 


2 


April. 


3 


April to May. 


4 


Do. 


5 


Do. 


6 


May to June. 


7 


Do. 


8 


Do. 


9 


June. 


10 


Do. 


11 


September to October. 


12 


June to October. 


13 


June to September. 


14 


Do. 


15 


August. 


16 


July to September. 


17 


Do. 


18 


July. 







1 Maximum, 20 days. 



2 About 20. 



3 Minimum, 6 days. 



Many of the lots contained a very small number of individuals, 
but in the main the incubation stage became progressively shorter 
as the average temperature rose. Between the temperatures of 56.8° 
and 62° F. the incubation periods are rapidly reduced, while between 
62° and 73.2° the reduction is much less rapid in proportion to the 
rise in temperature. This is a somewhat similar condition to that 
found in the cellar records. 

It is evident that the stage was shortest during the months of July 
and August, and longest during the months of March and April. 
Records began as early in the year as March 31, and closed as late 
as October 5. Two of the individuals in lot 1 incubated in the maxi- 
mum period of 20 days (Mar. 31 to Apr. 20) under an average tem- 
perature daily of 56.8° F. The minimum of six days was reached 
by 17 individuals in each of the months from June to September 
under average daily temperatures of from 66° to 73.2° F. 

The condition of food had no apparent effect upon the duration 
of the egg stage. Eggs deposited by radicicoles which had developed 
from eggs deposited by gallicoles received from Virginia incubated 
in the same average period as those descended from radicicoles of 
many generations, and eggs deposited by nymphicals incubated pre- 
cisely as did those laid by normal radicicoles. Individual incubation 
records, both of eggs reared in the laboratory cellar and of others 
reared on living vines, are given in connection with the development 
of the radicicoles under the same conditions in the section on " De- 
velopment of the radicicole larva," pages 54, 55, 57, 60-62, and 63. 



52 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

METHODS OF REARING THE RADICICOLE LARViE. 

During 1911 and 1912 the radicicoles were reared exclusively, both 
within and without an electric incubator, in the cellar. The roots 
on which the phylloxerse were reared were kept in glass jars and in 
petri dishes with moistened filter paper. This method was not always 
satisfactory, since it was not easy to maintain an even humidity 
similar to that existing under natural conditions. 

In 1913, 1914, and 1915 the insects were reared in the cellar and in 
the cages described below. The jars in the cellar were moistened by 
a layer of wet sand placed in the bottom. This method was more suc- 
cessful than in the case where moistened paper was utilized ; the roots 
did not decay or dry up so rapidly, and they remained in much bet- 
ter condition through the winter. 

These cages (Pis. V; VI, fig. 1; VII), constructed to hold young 
vines, may be described as follows: A trench 3 feet deep was dug 
wide enough to hold the cages with a space about 1 inch wide on each 
side. To prevent air passing down the cracks, small blankets were 
laid across the spaces, and this resulted in a temperature inside the 
cages of scarcely greater fluctuation than normally occurred 2 feet 
underground. The cages themselves were made of paraffined pine 
with an extra redwood bottom, and had two compartments, one above 
the other (PL VII). The upper compartment had on each side one, 
and the lower two, detachable boards the whole length of the major 
sides, and these boards were detachable to permit examination of 
of the roots and the removal of the pots. The upper compartment 
contained one and sometimes two pots (8 or 9 inches in diameter), 
around the top of which was fitted the topmost board of the cage, the 
outside measurements of which were 22 by 13 by 27* inches. The 
lower compartment contained 9-inch pots in saucers. 

The method of planting the vines in the pots of the cages was as 
follows : Into the middle board of the cages were fastened one or two 
saucers having holes bored through them. A short piece of glass 
tubing larger inside than the diameter of the roots was fixed into 
these holes with a cone of paraffin. Two .half pots, bottomless, were 
bound together by wire or tin bands to make a single whole pot, and 
placed to rest on the saucer. The vine was then put in place, certain 
of its roots being passed through the holes in the saucer and protrud- 
ing below. The upper pot was then filled with soil with a thin top 
layer of fine sand. In the lower compartment, whole 9-inch pots, one 
or two, as the case might be, were put in place in their saucers, and 
the protruding roots planted in them, at the surface of the soil 
passing through about 3 inches of glass cylinder. The surface of 
the soil in the lower pots was covered in most cases with a thin 
laver of fine sand. Fine sand was tamped into the glass cylinders, 



Bui. 903, U. S. Dept. of Agriculture. 



Plate V. 




The Grape Phylloxera in California. 

General view of pit and rearing boxes employed in life-history studies of the grape Phylloxera. 



Bui. 903, U. S. Dept. of Agriculture. 



Plate VI. 




Fig. 1. — Pit with, rearing boxes, illustrating method of covering with quilted strips to preserve same 

temperature as in like depth of soil. 




Fig. 2.— Galvanized tin cans used in connection with studies of the underground diffusion of 

Phylloxera. 

The Grape Phylloxera in California. 



Bui. 903, U. S. Dept. of Agriculture. 



Plate VII. 




The Grape Phylloxera in California. 

Rearing box drawn up from pit; sides of box removed. 



THE GRAPE PHYLLOXERA IN" CALIFORNIA. 53 

and those in the saucers above were also plugged with cotton. This 
procedure tended to prevent the phylloxeras from leaving the exposed 
portion of the root between the saucer of the upper pot and the 
surface of the lower. This exposed portion of living root averaged 
about 4 inches in length. 

Scaffolding was built above the trench and a rope and pulleys pro- 
vided in order that the cages might be raised and set in place on the 
stand for examination of roots. Electric connections were also pro- 
vided so as to enable the cages to be examined after dark. 

The cages above described were designed by R. L. Nougaret. 

DEVELOPMENT OF THE RADICICOLE LARVA. 

The young radicicole larva (PI. IX, g, A, p. 64), upon hatching 
from, the egg, seeks a place on the root where it may implant its beak 
and settle down to feed. During the summer some of the newly 
hatched larvae desert the vine and go in search of other vines, travel- 
ing either through cracks in the soil or over its surface. Newly hatched 
larvae are very active at all times and, being flat, can go through 
very small passages. Considering only those that remain on the 
vine on which they were born, it is found that the length of time 
elapsing between the hatching and settling on the root surface varies 
according to conditions of food at hand. On a decaying root the 
insect may not find a location for several hours, but if the root is 
sound the larvae mostly settle down immediately close by the egg- 
shells. 

A certain percentage of larvae always wanders about on the roots 
before finally settling. Many of these make their way outward and 
downward to the smaller rootlets, while others (mostly of the hiber- 
nant generation) in the fall make their way up to the bases of the 
larger roots and even to the main trunk. Larvae hatching on a 
decayed root usually leave it, but occasionally they remain and die 
of starvation. Observations on pieces of severed roots kept under 
cellar conditions indicated very little movement of the young larvae, 
provided their food was in good condition and they were not too 
much ©rowded. In the summer, however, large numbers deserted 
the roots in a manner similar to that observed in the vineyards, and 
these were apparently imbued with a wandering instinct. 

On vinifera vines young larvae prefer to settle on succulent parts 
of roots or rootlets. When they settle on growing rootlets, they 
generally cause the formation of nodosities, and on the roots of one 
or more year's growth the formation of tuberosities. They fre- 
quently settle on lesions already formed by older phylloxerae, and 
sometimes they settle and mature on the root without causing any 
perceptible lesion. When no lesion is formed, the insects develop 



54 



BULLETIN 903, U. S. DEPARTMENT OE AGRICULTURE. 



slowly, and as a rule the larger and more fleshy the lesion the more 
rapid is the growth of the insect thereon. On resistant vines the 
newly hatched larva rarely fastens on any place except the apex 
of the rootlet or on a nodosity already formed. On American non- 
resistant vines the larva? settle in the main as they do on viniferae, 
but on some varieties a decided preference is given to the growing 
rootlets over the larger roots. 

During the years 1911 and 1912 experiments were conducted to 
determine the growth and development of radicicoles under cellar 
conditions. Table X summarizes these observations. 



Table X. — Summarized records of incubation and development of the radicicole 
of the grape phylloxera under cellar conditions, during 1911 and 1912, Walnut 
Creek, Calif. 





Num- 
ber of 
indi- 
vid- 
uals. 


Incubation period. 


Num- 
ber of 
indi- 
vid- 
uals. 


Developmental 
period. 


Num- 
ber of 
indi- 
vid- 
uals. 


Generation cycle. 


Aver- 
age 
tem- 


Generation. 


Maxi- 
mum. 


Mini- 
mum. 


Aver- 
age. 


Maxi- 
mum. 


Mini- 
mum. 


Aver- 
age. 


Maxi- 
mum. 


Mini- 
mum. 


Aver- 
age. 


pera- 
ture 
during 
period 
of de- 
velop- 
ment. 


1 


49 

58 
21 
10 


Days. 
17 
13 
12 

18 


Days. 
10 

8 

8 

7 


Days. 
13.6 
10.2 
10.1 
13.3 


181 

352 

30 

8 

13 

18 


Days. 
48 
61 
41 
24 
208 
45 


Days. 
13 
16 
16 
17 
125 
14 


Days. 
29.6 
31.7 
26.6 
21.9 

183.0 
27.6 


49 

58 

21 

8 


Days. 
56 
74 
52 

38 


Days. 
26 
25 
26 
24 


Days. 
40.5 
42.2 
37.2 
34.6 


°F. 
63 


2 


64 


3 


64?; 


4 


64 


4i... 




5-9 2 . . . 


3 


12 


11 


11.3 


3 


41 


35 


37.3 









i Hibernating individuals, maturing in 1912. 

2 In 1912 the records extend from Mar. 20 to July 22. 

A summary of the observations made on the growth and develop- 
ment of the radicicole on severed root cuttings in the cellar in 1911 
and 1912 may be given in brief. The great variation existing in 
the growth of individuals under the same temperatures, and even on 
a given piece of root, is resultant entirely from the condition of the 
food. An aphid living on a callus formation or tuberous lesion 
develops more rapidly than one living on the normal surface of 
the same piece of root. Individuals living on vigorous roots de- 
velop more rapidly than those on decayed or dying roots. Oc- 
casionally a decaying root will send out very fleshy lesions, and 
these, while they remain fresh, provide ample nourishment for the 
aphids and enable them to grow quickly. After a root reaches a 
certain point in decay or dryness the phylloxerse can no longer de- 
velop on it and must seek better food or perish. 

The growing period of the aphids recorded in Table X ranged 
from 13 to 61 days, hibernating individuals excluded. The grand 
average, hibernants not considered, was 30.57 days, practically one 
month. That the maximum period may be prolonged is evidenced 
from an observation made in the summer of 1912, in which a series 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



55 



of individuals lived from 90 to 105 days on a particularly innutri- 
tious piece of root without maturing. 

During 1913 two series of further experiments were undertaken. 
One series was reared in the cellar and the other in an electric in- 
cubator, the latter under somewhat higher temperatures. Genera- 
tions were followed from May to October. Table XI summarizes 
these observations. 

Tarle XI. — Development of radicicoles of the grape phylloxera , Walnut Creek, 

Calif., 1913. 



Environment. 


Genera- 
tion. 


Number 
of indi- 
viduals. 


Average 
period of 
growth. 


Average 
tempera- 
ture. 


Cellar 


1 
2 
1 
2 
3 


44 
10 
15 
24 
3 


37.25 
32.40 
35.60 
28.80 
29.70 


°F. 
65.1 


Do 


69.8 


Incubator 


65.6 


Do. . 


71.1 


Do 


70.3 







From this table it is noticeable that temperature exerted consider- 
able influence on the growing period of the aphids, and that warmth 
accelerated their development. In a series of generations reared in 
1915 on very nutritious food, recorded under the heading " Maximum 
and minimum generations yearly " (p. 71) , this temperature influence 
is very apparent. The greater constant warmth in the incubator in- 
duced the aphids to remain active later in the fall, after those in the 
cellar had hibernated. In comparing the 1913 series with those of 
1911, it was found that the aphids of the former developed more 
slowly than did those of the latter, and this notwithstanding the fact 
that both the series of 1913 enjoyed higher temperatures than did the 
cellar series of 1911. The roots supplied in 1913 were of much poorer 
quality than were those supplied in 1911. 

Development on living roots, 1913-1915. — During 1913, 1914, and 
1915 the habits and development of the radicicoles were observed on 
living roots of vines growing in cages (Pis. V; VI, fig. 1; VII) kept 
in a trench where the temperature approximated that obtaining 
beneath the surface of the soil. As far as the temperature was con- 
cerned, the monthly averages ranged less than did those obtaining 
about 2 feet below the soil surface, but the daily fluctuations were 
considerably in excess of those in the soil. In the cages the roots were 
subjected to an average daily fluctuation of about 3° F. in summer 
and about 2° F. in winter. Two feet beneath the surface, the tempera- 
ture never fluctuated more than 1° in any given day. As far as could 
be observed, this temperature fluctuation had little effect on the 
growth of phylloxeras, except that it seemed to cause the nodosities to 
decay more rapidly than they would normally. Occasionally it was 
noted that some nodosities would dry up quickly after the cage had 



56 BULLETIN 903, IT. S. DEPARTMENT OF AGRICULTURE. 

been examined and its interior subjected for a few minutes to a tem- 
perature several degrees in excess of that obtaining in the trench 
immediately preceding the examination. 

Plate VII illustrates the details of the cages used for observing 
the phylloxera on living roots. By means of the pulley and stand 
the cages were hauled up and set for examination. It is obvious that 
only young vines could be used for this work, as 9-inch pots were the 
largest used. The vines were planted in early spring, certain of the 
longer roots, drawn through holes cut in the saucer supporting the 
bottomless upper pot, being planted in the lower pots. Thus about 
4 inches of root between upper and lower pots were available for 
inoculation and observation. At the upper and lower ends of this 
visible portion the root passed through glass cylinders, and the inter- 
vening spaces between the root and cylinder were filled with sand 
and cotton (sand only was used in the lower cylinders) to prevent 
the escape of phylloxeras to the invisible portions of the roots, both 
above and below. For the viniferas and nonresistant American 
vines this, however, failed to answer the purpose in many cases. 
Out of 22 upper pots, which were examined several months after 
the exposed roots were inoculated and had suffered more or less 
severe infestation, 18 developed infestation on their roots, show- 
ing that phylloxeras had found their way up to the roots in the 
upper pots. Out of 36 lower pots liable to infestation on their 
roots by reason of the fact that the exposed portions of the roots 
above were infested, the roots in 9 showed no infestation or indi- 
cations of any previous infestation, whereas in 13 others infestation 
occurred which had resulted from larvae successfully penetrating the 
lower glass cylinders ; in the remaining 14 pots, infestation or signs of 
previous infestation occurred resulting from wanderers reaching the 
rootlets by penetrating cracks in the soil. In the case of the re- 
sistants, the cylinders of sand and cotton packed between roots and 
glass were effectual in preventing spread to the invisible portions 
of the roots. On these vines the infestation was always very slight, 
and the phylloxeras exhibited very little desire to travel. On a 
Champini (rupestris X candicans), on which the phylloxeras in- 
fested only the side rootlets, and which bore only a slight infesta- 
tion, wandering larvas entered the soil and infested the rootlets of 
one of the lower pots, but there was no penetration through the glass 
cylinders. 

As temperature is a factor of importance in the development 
of the phylloxera, the following comparisons (Table XII) of tem- 
peratures are noteworthy, taken (1) inside the cages containing 
living vines, (2) 2 feet below the soil surface, at a point in the 
laboratory vineyard a few feet distant from the trench containing 
the cages aforesaid, and (3) in the laboratory cellar: 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



57 



Table XII. — Comparative monthly average temperatures ; inside cages in trench, 
2 feet below soil surface in laboratory vineyard, and in laboratory cellar. 
Walnut Creek, Calif. 



Month. 


Two feet 

below 

surface. 


In cages 

in 
trench. 


In labo- 
ratory 
cellar. 


1913. 
May.. ; 


°F. 


°F. 

159 
68 
71 
71 
69 
65 
56 
49 

52 
52 

56 
58 
63 
68 
72 
72 
66 
64 
56 


°F. 








July 


76 

77 

77 

70.5 

64 

53 

54 

51 

58 

62 

65.5 

70 

72.5 

74 

70.5 

66 

58.5 

50.5 

49 

52 

57 

62 

63.5 

71.5 

75.5 

75 

71.5 

66 




August 




September 


68 


October 


63 


November 


59 


December 


56 


1914. 
January 


55 


February 


55 


March 


58 


April 


59 


May 


62 


June 


65 


July 


67 


August 


69 


September 


67 


October 


63 


November 


58 


December 


54 


1915. 
January 




54 


February 




55.5 


March 


56.5 

57 

59 

68 

73 

73.5 

69 

64.5 


57 


April 


58 


May , 


60 


June 


65 


July 


68 


August , 


69 


September 


66 


October 


62 







1 Approximate. 

Examination of Table XII indicates that the cellar temperatures 
showed the least annual variation and that the average temperatures 
in the soil for every month, except February, 1914, exceeded the 
corresponding temperatures in the cages. It is probable, leaving 
other factors out of consideration, that the accumulated excess of 
heat in the soil over that in the cages throughout one season would 
produce an extra generation of phylloxera, besides prolonging the 
active development later into the autumn. The summer of 1913 
was much warmer than that of the year following. This is borne 
out by the soil temperature comparisons, but does not appear from 
the cage temperatures. 

To obtain life-history data, the following vines were used : Burger, 
Muscat, Thompson's Seedless, Mission, Champini, and Grenache. On 
the Champini the phylloxeras refused to settle, except on fleshy 
side-rootlets, but on the others they settled at any point. On the 
Grenache roots, however, several of the inoculations proved unsuc- 
cessful, the young larvae not settling. On the others, inoculations 
nearly always proved successful. Inoculations were made by transfer- 
ring eggs from one root to another with a camel's-hair brush. Since 
the roots in all cases were vertical, or very nearly so, it happened 



58 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

occasionally that some of the eggs used in the inoculations dropped 
off. This was unavoidable, and when egg-laying females Were 
under observation it frequently happened that the eggs dropped 
down. When more than one female was producing eggs simul- 
taneously on a single root, there even arose doubt as to which certain 
of the fallen eggs should be credited. For the biological records 
the first season, 9 vines were used, averaging 3 separate roots each, 
but since 3 of these roots died, after they were planted, only 24 
roots were actually used. Of these 3 were used for rearing gallicole 
progeny and 5 others were used for nymph production and ferti- 
lizer experiments on heavily infested vines, leaving 16 for individual 
records. In 1914 and 1915, only 4 vines were used each year to con- 
tinue the individual series. 

Many interesting habits were observed, but the behavior of the 
phylloxerae in the main did not differ from that observed under 
cellar conditions upon severed roots. Newly hatched larva? mostly 
settled close to the eggshells they had vacated, but if there were 
any fresh lesions near by, the young larvae often found their way 
to them and settled. Occasional movements of older individuals 
were observed, not only at the time of molting but at any time in 
the instars. These movements were generally in the direction of 
more succulent food. Occasionally egg-laying individuals shifted 
their positions without apparent injury, although this was some- 
times followed by a temporary halt in the production of eggs. The 
production of nymphs occurred from June to October, as in the vine- 
yard. The tendency of the nymphs to crawl up the root just before 
transforming was noticeable. Most of them could go no farther up- 
ward than the cylinder plugged with cotton, and so perforce had 
to transform into migrants at this point. A small percentage trans- 
formed at points farther down the root and did not appear to have 
made any upward migration. On the heavily infested roots, wan- 
derers appeared from July to October. These roamed around the 
inside of the compartment, and succeeded in finding their way down 
through cracks in the soil of the lower pots, and infested the root- 
lets, especially those growing against the inside of the pots. After 
irrigation, cracks appeared in the soil around the inside of the pot, 
furnishing the wandering larvae access to the rootlets. In no case 
was this infestation of any great extent, although large numbers of 
wandering larvae were observed in several of the cages, and only a 
very small percentage, presumably, found their way to a new food 
supply. This fact has an important bearing upon the distribution 
of the insect as will be noted elsewhere. Although it appeared dif- 
ficult for the insects to penetrate an inch of sand in the lower glass 
cylinder, the occurrence of large infestations immediately below the 
cylinder, coupled with evidences of only slight infestations on the 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 59 

rootlets around the inside of the pots, showed that such a penetration 
had occurred. It was obvious in these instances, few though they were, 
that the heavy infestations could not have resulted from inoculations 
on rootlets from wanderers, because only a few nodosities occurred 
on the rootlets, showing a slight wanderer infestation, and not 
enough time had elapsed in the interim for the infestation present 
at the date of examination to be produced by so small a company of 
wandering larva?. The phylloxera? had no difficulty in finding their 
way through the upper cylinder to the root system of the upper pots 
through layers of cotton and sand each about half an inch thick. 
On the roots of the upper pot of cage V, Burger, there were, on 
November 26, 1913, upward of 1,600 hibernants disposed in large 
clusters on the main root. Since June of that year, the visible por- 
tions of four roots below had been well infested. Every one of those 
1,600 hibernants was the progeny of phylloxera? hatched on the visi- 
ble part of the roots and which had penetrated the upper cylinders. 
It is obvious that a great many individuals penetrated the cylinders, 
as the scarcity of lesions showed that the greater part of the in- 
festation was comparatively recent. Apparently a natural law 
against overcrowding comes into play, and migration was encouraged 
by the fact that the tuberosities on three of the four roots had become 
rotted and threatened to decay all the visible portions of those roots. 
As, on this vine, no infestation other than a few nodosities occurred 
below the cylinders in the lower pots, it would appear that the heavy 
migration had been entirely in an upward direction. As far as could 
be determined, there appeared no reason why the insects could not 
penetrate the lower cylinders just as easily as the upper ones, so the 
conclusion is that in most cases they did not make the attempt. 

In the instances wherein phylloxera? had undoubtedly penetrated 
the lower cylinders they were found to be close to the cylinder as 
if the packing of sand and cotton had been so loose that no effort 
was needed for the insect to force its way through. The sand 
in the upper cylinders, by reason of the weight of earth pressing 
upon it, always remained well packed and presented a barrier to the 
progress of the phylloxera?. That they were able to surmount this 
barrier is shown by the large numbers present, and indicates that 
the upward migration was a well-defined movement. The possibility 
presented itself that infestations on the roots of the upper pots could 
have originated from wandering larva? that had penetrated the 
soil of the upper pots in the same manner as they had obviously done 
in the lower pots of the cages. The absence of. cracks except around 
the periphery of the soil in the pots and of nodositous infestations 
on the rootlets below taken in conjunction with the size of the infesta- 
tions precludes this as the sole source of the inoculations of the upper 
pots. 



60 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



Some of the lower pots of the cages were filled with quartz of 
mixed grades. This was done chiefly for the purpose of experi- 
menting with liquid fertilizers as to the bearing of fertilizing 
substances upon the behavior of infested vines as an adjunct to 
similar vineyard experiments. Twelve out of 36 lower pots con- 
tained quartz. It was found that the wandering larvae were able 
to descend to rootlets growing in the quartz as easily as to those 
growing in earth. On the other hand, the phylloxeras were not able 
to exist on the larger roots in the quartz in appreciable numbers, 
as it appeared that they could not pass through the quartz when it 
was packed around the root. This is similar to the condition existing 
on very sandy soils, wherein the phylloxerae are unable to travel 
when the sand becomes packed around the roots. 

Table XIII indicates the incubation and development of the 
radicicoles on the roots of living vines. 

Table XIII. — Incubation and development of radicicole of the grape phylloxera 
on living vines, Walnut Greek, Calif., 1913-1915. 

FIRST GENERATION, 1913. 



Indi- 
vidual 
No. 



1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

2S 

29 
30 
31 

32 
33 
34 
35 
36 
37 
38 
39 
to 

41 
42 
13 
44 
45 



Date egg 
deposited. 



Apr. 29 

May 28 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 

June 14 
...do.... 
...do.... 
...do.... 
...do.... 

June 15 
...do.... 
...do.... 

June 16 

June 8 
...do.... 
...do.... 

...do 

...do.... 
...do.... 
...do.... 
...do.... 

...do 

...do.... 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 

May 25 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 



Date egg 
hatched. 



May 14 

June 6 
...do... 
...do... 
...do... 
...do... 
...do... 
...do... 
...do... 

June 22 
...do.... 

June 23 

June 22 

June 24 
...do... 
...do... 

June 26 
...do... 

June 17 
...do... 

June 19 
...do... 

June 20 

June 17 
...do... 

June 18 
...do... 
...do... 
...do... 
...do... 
...do... 
...do... 
...do... 
...do... 

June 4 
...do... 

June 5 
...do... 

June 6 
...do... 
...do... 
...do... 
...do... 

June 8 
...do... 



Incuba- 
tion 
period. 



Days. 



15 
9 
9 
9 
9 
9 
9 
9 
9 



9 
8 

10 

9 

9 

11 

10 

9 

9 

11 

11 

12 

9 

9 

10 

10 

10 

10 

10 

10 
10 
10 
10 
10 
10 

11 
11 

12 
12 
12 

12 
12 
14 
14 



Date 

insect 

matured. 



June 8 
June 25 

...do.... 
June 26 
June 28 
June 29 
June 30 

...do.... 

...do 

July 5 
Julv 8 
July 7 
July 9 
July 14 

...do.... 
July 15 
July 18 
July 21 
July 9 

...do.... 
July 13 

...do.... 
July 15 
July 7 
July 8 
July 2 

...do.... 

...do.... 
July 4 
July 6 

...do.... 

...do.... 
July 7 

...do.... 
June 19 
June 21 
June 23 
June 24 
June 25 

...do.... 
June 27 

...do.... 
June 29 
July 2 
July 3 



Growing 
period. 



Days. 



25 
19 
19 
20 
22 
23 
24 
24 
24 
13 
16 
14 
17 
20 
20 
21 
22 
25 
22 
22 
24 
24 
25 
20 
21 
14 
14 
14 
16 
18 
18 

18 
19 
19 
15 

17 

18 

19 
19 

19 
21 
21 
23 
24 
25 



Total 
period of 
develop- 
ment. 



Days. 



40 
28 
28 
29 
31 
32 
33 
33 
33 
21 
24 
23 
25 
30 
29 
30 
33 
35 
31 
31 
35 
35 
37 
29 
30 
21 
24 
21 
26 
28 
28 

28 
29 
29 
25 
27 
29 
30 
31 
31 
33 
33 
35 
38 
39 



Variety of vine and 
number of cage. 



Mission VII. 

do 

do 

do 

do 

do 

do 

do 

do 



Burger VI . 

do 

do 

do 

do 

do 

do.... 

do.... 

do 

Burger V . 

do 

do 

do 

do 

do 

do.... 

do.... 

do.... 

do 

do 

do.... 

do 

do.... 

do.... 

do.... 

do.... 

do 

do.... 

do 

do.... 

do.... 

do.... 

do.... 

do.... 

.....do.... 
....do.... 



Average 
temper- 
ature. 



F. 



60 
67 
67 
67 
67 
67 
67 
67 
67 
69 
69 
69 
69 
69 
69 
69 
69 
69 
68 
68 
69 
69 
69 
68 
68 
68 
68 
68 
68 
68 
68 
68 
68 
68 
67 
67 
67 
67 
67 
67 
67 
67 
68 
68 
68 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



61 



Table XIII. — Incubation and development of radicicole of the grape phylloxera 
on living vines, Walnut Creek, Calif., 1913-1915 — Continued. 

SECOND GENERATION, 1913. 



Indi- 
vidual 

No. 



1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

-13 

14 

U5 

16 

17 

18 

19 

20 

21 

22 

23 

124 

25 

26 

127 

128 

129 

130 

131 

132 

133 



Date egg 
deposited. 



June 10 
June 11 
June 12 
...do.... 
June 30 

...do 

...do.... 

...do 

...do.... 

...do.... 

...do.... 

...do.... 

July 1 

...do.... 

...do.... 

June 30 

June 26 

...do.... 

...do 

...do 

...do.... 

...do 

...do.... 
June 27 

...do 

June 30 
...do.... 

...do 

...do.... 
July 1 
...do.... 
July 2 
...do.... 



Date egg 
hatched. 



June 20 
June 19 
...do... 
June 20 
July 6 
July 8 
...do... 
...do... 
...do... 
July 9 
...do... 
...do... 
...do... 
...do... 
...do... 
...do... 
July 3 
July 4 
...do... 
...do... 
...do... 
July 5 
...do... 
July 4 
July 5 
...do... 
July 6 
July 7 
...do... 
July 8 
...do... 
...do... 
July 10 



Incuba- 
tion 
period. 



Days. 



10 
8 
7 
8 
6 



Date 

insect 

matured. 



July 8 
...do.. . 
...do... 
July 11 
July 20 
July 22 
July 23 
...do... 
July 31 
July 24 
July 25 
July 31 
Aug. 4 
Aug. 7 
Aug. 11 
Aug. 8 
July 21 
July 25 
July 26 
...do... 
July 28 
July 29 
July 31 
July 28 
July 31 
Aug. 8 
Aug. 10 
Aug. 12 
...do... 
...do... 
Aug. 13 
Aug. 14 
Aug. 18 





Total 


Growing 


period of 


period. 


develop- 




ment. 


Days. 


Days. 


18 


28 


19 


27 


19 


26 


21 


29 


14 


20 


14 


22 


15 


23 


15 


23 


23 


31 


15 


24 


16 


25 


22 


31 


26 


34 


29 


37 


33 


41 


30 


39 


18 


25 


21 


29 


22 


30 


22 


29 


24 


32 


24 


33 


26 


35 


24 


31 


26 


34 


23 


29 


35 


41 


36 


43 


36 


43 


35 


42 


36 


43 


37 


43 


39 


47 



Variety of vine and 
number of cage. 



Mission VII 


68 


do 


68 


do 


68 


do 


69 


do 


70 


do 


70 


do 


70 


do 

do 


70 
71 


do 


70 


do 


70 


do 


71 


do 


71 


do 


71 


do 


71 


do 


71 


Burger VI 


70 


do 


70 


...I.do 


70 


do 

do 


70 
70 


do 


70 


do 


70 


do 


70 


do 


70 


Burger V 


71 


do 


71 


do 


71 


do 

....do 


71 

71 


do 


71 


do 


71 


do 


71 



Average 
temper- 
ature. 



THIRD GENERATION, 1913. 



1 

2 
3 

4 


July 23 
July 28 
July 29 
...do 


July 31 
Aug. 5 
Aug. 7 
...do 


8 
8 
9 
9 

10 


Aug. 25 
Aug. 28 
Aug. 30 
Sept. 1 
Sept. 3 


25 
23 
23 

25 
26 


33 
31 
32 
34 

36 


5 


...do.... 


Aug. 8 



Thompson's Seedless I. 

Muscat IV 

....do 

....do 

....do 



71 
71 
71 
71 
71 



FOURTH GENERATION, 1913-14. 



1 


Aug. 26 
Sept. 1 

...do.... 


Sept. 3 
Sept. 8 
Sept. 9 
Sept. 10 
Sept. 23 


8 
7 
8 
9 


( 2 ) 
Sept. 18 
Sept. 22 
Sept. 30 
Apr. 6 
Apr. 9 
Oct. 24 
Apr. 6 
Apr. 7 
May 20 
Apr. 15 
Apr. 24 
Apr. 28 






Thompson's Seedless I . . 
Champini IX 


371 


2 


10 

13 

20 

195 

198 

30 

194 

195 

238 

203 

211 

215 


17 
21 
29 


70 


3 


do 


69 


4 


....do 


69 


5 


Muscat IV 




6 








do 




7 




Sept. 24 
...do 






do 


66 


8 








..do 




9 




...do 






..do 




10 




...do 






....do 




11 




...do 






..do 




12 




Sept. 25 
...do 






..do 




13 








..do 



















FIFTH GENERATION, 1914. 



1 


Apr. 25 

Apr. 26 

...do 


May 9 

...do 

...do 


14 
13 
13 
12 
12 
11 
11 


May 28 

...do 

June 2 
June 1 
June 2 

...do 

June 3 


19 
19 
24 
23 
24 
24 
25 


33 
32 
37 
35 
36 
35 
36 


Muscat IV . ^ 


62 


2 
3 


do 

...do 


62 
63 


4 
5 


Apr. 27 
...do 


...do 

...do 


do 

..do 


63 
63 


6 

7 


Apr. 28 
...do 


...do 

...do 


do 

do 


63 
63 













1 Indicates winged migrants. 2 Hibernant. 3 Indicates average temperature of incubation period alone. 



62 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



Table XIII. — Incubation and development of radicicole of the grape phylloxera 
on living vines, Walnut Creek, Calif., 1913-1915 — Continued. 

SIXTH GENERATION, 1914. 



Indi- 
vidual 

No. 


Date 
egg de- 
posited. 


Da f e 

egg 

hatched. 


Incuba- 
tion 
period. 


Date 

insect 

matured. 


Growing 
period. 


Total 
period of 
develop- 
ment. 


Variety of vine and 
number of cage. 


Average 
temper- 
ature. 


1 


May 29 
June 2 
June 9 
...do 


June 7 
June 8 
June 19 
June 20 


Days. 

9 

6 

10 

11 


June 24 
July 1 
July 10 
July 26 


Days. 
17 
23 
21 
36 


Days. 
26 
29 
31 

47 


Muscat IXA 


° F. 
67 


2 


Grenache IIA 


68 


3 


Muscat IXA 


69 


4 


do 


69 









SEVENTH GENERATION, 1914. 



June 24 

...do 

June 25 

...do 

June 26 
...do..... 
July 1 
July 2 
...do..... 
July 3 
...do 



July 3 
July 4 
July 3 
July 4 

...do..... 

...do..... 
July 9 
July 11 

...do..... 

...do..... 

...do 



9 


July 23 


20 


29 


10 


July 29 


25 


35 


8 


July 23 


20 


28 


9 


July 30 


26 


35 


8 


July 28 


24 


32 


8 


July 30 


26 


34 


8 


July 29 


20 


28 


9 


...do 


18 


27 


9 


Aug. 1 


21 


30 


8 


Aug. 3 


23 


31 


8 


...do 


23 


31 



Muscat IXA . . 

do 

do 

do 

do 

do 

Grenache IIA . 

do 

do 

do 

do 



70 
71 

70 
71 
71 

71 
72 
72 
72 
72 
72 



EIGHTH GENERATION, 1914-15. 



Aug. 17 
..do 


Aug. 24 
...do 


7 
7 
8 
8 
8 
8 
8 
8 
9 


...do 
. .do 


Aug. 25 
...do 


..do 


...do 


..do 


...do 


..do 


...do 


..do 


...do 


...do 


Aug. 26 



Sept. 16 

" Sept* 26 
Mar. 26 
Mar. 30 
Apr. 3 
Apr. 4 

( 4 ) 

( 4 ) 



23 
23 
32 
213 
217 
221 
222 



30 
30 
40 
221 
225 
229 
230 



Muscat XXX. 

do 

do 

do 

do 

do 

do 

do 

do 



70 
70 
69 
3 72 
3 72 
3 72 
3 72 
s 72 
3 72 



NINTH GENERATION, 1914-15. 



Sept. 16 



Sept. 27 
...do 



11 
11 



( 4 ) 
Apr. 11 



196 



207 



Muscat XIX. 
do 



3 72 
3 72 



NINTH GENERATION, 1915. 



1 

2 


Mar. 31 
...do 
...do 

..do 


Apr. 19 

...do 
...do 


19 
19 
19 
19 


May 22 
May 23 
May 24 
May 25 


33 
34 
35 

36 


52 
53 
54 
55 


CarignanXXIX 

do 


57 
57 


3 


do 


57 


4 


...do 


57 













TENTH GENERATION, 1915. 



1 


May 23 


June 3 


11 


June 24 


21 


32 


2 


May 27 


June 6 


10 


July 1 


25 


35 



Carignan XXIX... 
Zinfandel XXIIIA. 



66 
67 



ELEVENTH GENERATION, 1915. 



July 9 



July 15 



Aug. 10 
July 29 
...do..... 



26 



32 



Zinfandel XXIIIA. 
Carignan XXIX... 
do 



73 



TWELFTH GENERATION, 191: 



1 

2 


Aug. 2 

...do.. . 

...do 

Aug. 4 

Aug. 16 

...do 

Aug. 17 

Aug. 18 

Aug. 19 


Aug. 9 
Aug. 10 
Aug. 9 
Aug. 11 
Aug. 24 
Aug. 25 

...do 

Aug. 27 

...do 


7 
8 
7 
7 
8 
9 
8 
9 
8 


Sept. 8 
Sept. 9 
Sept. 10 


30 
30 
32 
30 


37 
38 
39 
37 


Zinfandel XXXVI 
do 


72 
72 


3 


do 


72 


4 


...do 


72 


5 


Zinfandel XXIIIA.... 




6 








do 




7 








...do 




8 








...do 




9 








...do 

















:i Indicates average tomporature of incubation period alone. 



' Pied, 1915. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 63 

For the first generation, eggs deposited by adult hibernants were 
secured from a Zinfandel vineyard, and thereafter only eggs de- 
posited in the cages and of known generations were used in the inocu- 
lations. 

The average growing periods of the summer generations of wing- 
less aphids varied from 34.5 to 18.25 days, but in all except two gen- 
erations this period ranged between 18.25 and 24.20 days. Individ- 
uals varied between 36 and 10 days. The winged forms developed 
more slowly than the wingless, nine individuals averaging 34^ days- 
The hibernants developed in an average of 6f months. 

Eggs were placed for the most part on roots never before infested, 
and tuberosities usually followed rapidly after the hatching of the 
larvae. Nodosities were formed upon side rootlets. The main roots 
were all between one-sixth and one-third of an inch in diameter. 

It was found that about 40 per cent of the larvae remained on the 
exposed portions of the roots, the rest finding their way to the other 
portions. In spring a large percentage and in summer and autumn 
a smaller percentage of larvae settled close beside the eggshells from 
which they had issued. In spring the larvae did not display a tend- 
ency to roam, but in summer and autumn they wandered consid- 
erably, especially if the root had begun to decay or was drying too 
rapidly. Similar conditions occur in vineyards, and it is in summer 
and autumn that the typical wandering larvae are found. 

Excluding the winged migrants and the hibernated individuals, 
the summary of the growing period of all the phylloxeras developing 
on living roots during the years 1913, 1914, and 1915 is recorded in 
Table XIV. 

Table XIV. — Summary of Table XIII. 

Number of individuals 114 

Average period of growth days — 22.15 

Maximum period of growth do — 36 

Minimum period of growth do — 10 

Taking into consideration the individuals removed before they 
attained their full development, the average growing period is to be 
estimated at about 25 days. The cellar experiments with severed 
pieces of roots in 1911 and 1912 combined yielded an average of 
30.57 days, and the experiments in the cellar and incubator combined 
in 1913 averaged 34.16 days. The cellar temperatures of 1911 and 
1912 averaged about 1J° F. lower than the combined cage tem- 
peratures for the period 1913-1915 for the months from May to 
October, inclusive. The cellar temperatures for 1913 averaged about 
li° lower than the incubator temperatures for 1913 and about ^° 
higher than the cage temperatures for that year. 



64 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

In the cellar and incubator during 1913 the phylloxerae developed, 
on the average, more slowly than in the cellar during 1911 and 1912, 
notwithstanding higher temperatures in 1913. This resulted from the 
fact that the food supply was much more succulent in 1911 and 1912. 
Likewise the phylloxerae developed much more rapidly in the cages 
in 1913-1915 than in the cellar and incubator combined in 1913, 
when the temperatures differed slightly (the difference in favor of 
the cages being about 1° daily). This also was due to the superior 
food of the living vines. In comparing the phylloxera development 
in the cellar in 1911-12 with that in the cages in 1913-1915, it would 
appear that both temperature and food influenced the more rapid 
development observed in the cages. For 1911 alone the average grow- 
ing period was 29.37 days. This growth took place on succulent roots, 
to all appearances as succulent as the living roots upon which were 
reared the 1913-1915 phylloxerae, which averaged about a 25-day 
period, under a temperature averaging 4J° in excess of that obtain- 
ing in the cellar in 1911. It would be natural to ascribe the faster 
growth in the cages to the higher temperatures, but in view of the 
discrepancies noted above in connection with the 1913 cellar and 
incubator observations, the writers are inclined to belieA^e that the 
living roots afforded better nourishment to the phylloxerae than did 
the severed roots of 1911 and that the higher temperatures of 1913 
had less influence than might appear in bringing about such a dif- 
ference in the growing periods. 

Excepting for a few isolated instances, the phylloxerae on living 
roots developed more rapidly on nodosities and tuberosities than on 
the normal surface of the root. On nodosities development was the 
most rapid, noticeably more rapid than on tuberosities, and the more 
fleshy the swelling the more rapid was the aphid's growth. 

DESCRIPTION OF STAGES. 

The egg. — When first laid, the radicicole egg (Pis. VIII, g; IX, 
7c, I) is lemon yellow, about twice as long as wide, oval, both ends 
rather bluntly rounded, the micropylar end a little more abruptly 
so. Thirty-six eggs laid by newly matured adults August 30 and 
September 6, 1911, averaged 0.348 mm. in length and 0.173 mm. in 
width, with maxima, respectively, of 0.36 and 0.18 mm., and minima, 
respectively, of 0.34 and 0.17 mm. Of 25 eggs laid by overwintered 
radicicoles near the end of their laying period, the maximum length 
was 0.32 mm., the maximum width 0.18 mm., the minimum length 0.20 
mm., and the minimum width 0.12 mm., the average length 0.26 mm., 
and the average width 0.14 mm. Thus it appears that the size of the 
eggs laid by individuals decreases toward the end of their egg-laying 



Bui. 903, U. S. Dept. of Agriculture. 



Plate VIM. 




■m 



The Grape Phylloxera in California. 

Phylloxera vitifoliae: a-e, "Winged migrant; a, dorsal view, 6, antenna; c, basal sensorium of 
antennal segment III; d, hind leg; e, beak;/, male egg; g, radicicole egg; h, i, female eggs; 
j, k, I, sexed female;;', enlarged ventral vie^\ showing contained winter egg; fc, antenna; 
I, newly hatched female; m, mature male just after casting last skin. 



Bui. 903, U. S. Dept. of Agriculture. 



Plate IX. 




The Grape Phylloxera in California. 

Phylloxera vitifoliae: a. b, c, Adult, radicicole; n, ventral view (beak shown telescoped); 
b, dorsal view; c, antenna; d, e,f, hibcrnant larva; rf, dorsal view; e. ventral view; f . an- 
tenna; g, h, newly hatched (tirst-instar) radicicole: g, ventral view; h. dorsal view; 
i,j, second-instar radicicole;/, dorsal view; j, antenna: /.. /. radicicole egg corium; k, whole 
shell; I, section to show structure. 



Bui. 903, U. S. Dept. of Agriculture. 










The Grape Phylloxera in California. 

Phylloxera vitifoliae: a, b, c, Third-instar radicicole; a, dorsal view; b, ventral view; c, left 
antenna; d,e,f, prenymph (third instar of winged form); d, dorsal view; e, ventral view; 
/, left antenna; g-j, fourth-instar radicicole; g, dorsal view; h, left antenna; i, ventral view 
(beak shown telescoped);;', beak. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



65 



period. Toward the period of hatching the egg becomes darker and 
the eyespots of the embryo become visible. 

The larva. — In hatching, the young larva (PI. IX, </, h) splits 
the eggshell from the micropyle lengthwise to about three-fourths 
of its length. This splitting is more or less gradual and is caused 
by the thorax and head of the young phylloxera bursting the shell 
and then gradually enlarging the crack. The larva poises itself at 
an angle of 45°, with legs and antennae appressed to the body, and 
slowly eases its way out. It seems to rely simply on a slow side- 
wise body movement to free itself of the shell. When freed, it 
spreads the appendages and is then able to walk off. The newly 
hatched larva is of a pale lemon yellow, with dark claret-colored 
eyes, composed each of three circular facets and placed in the form 
of the angles of an equilateral triangle. The body segmentation is 
quite distinct, more so than in later instars. The shape is oval and 
very flat. The antennae, as in all forms of the grape phylloxera, are 
three-jointed. The terminal joint is twice as long as the two basal 
combined. Near the apex of the third joint occurs a circular sen- 
sorium. The beak in early generations reaches to the penultimate 
or antipenultimate body segment, and in later generations protrudes 
beyond the caudal segment of the abdomen. The legs and antennae 
bear hairs. Table XV gives measurements for five newly hatched 
individuals. 

Table XV. — Measurements of newly hatched radicicoles of the grape phylloxera, 

Walnut Creek, Calif., Oct. 23, WlJf. 



Individual No. 


Length 
of body. 


Maxi- 
mum 
width 
of body. 


Length 
of beak. 


Length 
of hind 
femur. 


Length 

of hind 

tibia. 


Length of antennal joints. 


Length 

of sen- 

sorium. 


1 


2 


3 


1 


Mm. 
0.359 
.327 


Mm. 
0.176 
.179 


Mm. 
0. 1964 
.2036 


Mm. 
0. 0679 


Mm. 
0. 0571 


Mm. 


Mm. 

0. 0161 
.0143 
.0196 
.0180 
.0188 
.0152 


Mm. 
0. 0705 
.0625 
.0680 
.0705 
.0634 
.0670 


Mm. 


2 


6. 0169 
.0214 
.0232 
.0188 
.0179 




3 


.0562 
.0580 
.0566 
.0554 


.0429 
.0491 
.0455 
.0491 




4 


.359 
.341 


.189 
.190 


.2152 
.2107 




5 


0.0231 


6 


.02?S 













The young phylloxera? hatching in spring have shorter beaks than 
those which hatch in the fall, the beaks in spring averaging in length 
about 0.155 mm. 

The first molt does not take place until more than half of the grow- 
ing period is passed. The molting of the radicicoles is a procedure 
quite similar in detail to the hatching from the egg. After each molt 
the individual for about 24 hours is brighter in color than at any 
other time during the instar. After the first molt the phylloxera 
changes from oval or suboval to pyriform in shape (PI. IX, i, j). 
1900°— 21 5 



66 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



Table XVI gives measurements for four individuals of the second- 
instar radicicole. 

Table XVI. — Measurements of second-instar radicicoles of the grape phylloxera, 

Walnut Creek, Calif. 



Individual No. 


Length 
of body. 


Maxi- 
mum 
width 
of body. 


Length 
of beak. 


Length 
of hind 
femur. 


Length 

of hind 

tibia. 


Length of antennal joints. 


Length 

of sen- 

sorium. 


1 


2 


3 


1 


Mm. 
0.419 

.448 
.439 
.499 


Mm. 
0.234 


Mm. 
0.154 


Mm. 
0. 0625 
.0624 


Mm. 
0. 0526 
.0518 


Mm. 
0.0190 
.0205 


Mm. 
0. 0204 
.0205 


Mm. 
0. 0586 
.0589 


Mm. 


2 




3 


.257 
.270 


1.113 

.168 




4 












0. 0171 












— 





i Telescoped. 

The roughened tubercular areas on the dorsal surface are more 
conspicuous after the first molt, and a rapid increase in bulk is 
apparent during the second instar. 

The second, third, and fourth molts occur at practically equidistant 
periods. Under highest temperatures and optimum food conditions, 
these instars are passed in about two days apiece. Under a tempera- 
ture of 58'° F. from three to eight days elapse between molts, the 
average being about five and one-half days. 

Table XVII gives the measurements of five individuals of the 
third instar. 

Table XVII. — Measurements of third-instar radicicoles of the grape phylloxera, 

Walnut Creek, Calif. 



Individual No. 1 


Length 
of body. 


Maxi- 
mum 
width 
of body. 


Length 
of beak. 


Length 
of hind 
femur. 


Length 

of hind 

tibia. 


Length of antennal joints. 


Length 

of sen- 

sorium. 


1 


2 


3 


1 


Mm. 

0.592 
.524 
.522 
.649 


Mm. 

0.303 
.312 
.332 
.355 


Mm. 

0.178 
.164 
.179 
.155 


Mm. 
0. 0699 


Mm. 
0. 0607 


Mm. 
0. 0202 
.0252 


Mm. 
0. 0321 
.0207 


Mm. 
0. 0616 
.0568 


Mm. 
0.0 


2 


.0144 


3 


.0739 
.0732 
.0758 
.0741 


.0622 
.0687 
.0660 
.0692 




4 


.0241 
.0197 
.0206 


.0205 
.0187 
.0194 


.0634 
.0589 
.0598 


* 




.0177 


5 


.648 


.371 


.145 


.0186 


6 


.0190 























1 Individuals 1-3, newly molted; 4, two days after molt; 5, three days after molt. 

During the third instar (PL X, a, b, c) the increase in bulk con- 
tinues rapidly. The dorsal tubercular areas are larger than in the 
previous instar, but in color and shape no differences appear. 

Table XVIII indicates the measurements of seven individuals of 
the fourth (penultimate) instar, 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



67 



Table XVIII. — Measurements of fourth-instar radicicoles of the grape phyl- 
loxera, Walnut Creek, Calif. 



Individual No. 1 


Length 
of body. 


Maxi- 
mum 
width 
of body. 


Length 
of beak. 


Length 
of hind 
femur. 


Length 

of hind 

tibia. 


Length of antennal joints. 


Length 

of sen- 

sorium. 


1 


2 


3 


1 


Mm. 

0.919 
.851 
.824 
.615 


Mm. 

0.517 
.528 
.579 
.500 


Mm. 


Mm. 
0.0848 


Mm. 

0. 0687 


Mm. 

0. 0321 
.0321 
.0276 
.0306 
.0297 


. Mm. 
0. 0259 
.0277 
.0241 
.0261 
.0248 


Mm. 

0. 0669 
.0571 
.0768 
.0748 
.0721 


Mm. 


2 






3 




.0830 


.0749 


0. 0212 


4... . 


0.172 
.162 
.160 


.0167 


5 






.0162 


6 


.753 
.700 


.426 


.0802 


.0671 




72 





























1 Individuals 1-3 were measured toward the end of the instar, and individuals 4-7 very shortly after 
molting. 
* Maximum height, 0.3 mm. 

A very obvious growth takes place during the fourth instar (PL X, 
g-j). At the end of this instar the phylloxera casts its last skin 
and issues therefrom as an adult. The adults, except immediately 
following the molt, are never as pale as the immature forms. They 
may be distinguished from fourth-instar individuals by two longi- 
tudinal furrows on the thorax and by the relatively larger dorsal 
tubercular areas. The color varies from a light green to a dark 
purplish brown in living specimens. This variation is to a great 
degree dependent on the food supply. On fresh, fleshy nodosities 
the insects mostly are pale green with the tubercular areas very 
noticeable. On tuberosities, or on the normal surface of a vigorous 
root, the color is yellowish green, olive green, or light brown, with 
the tubercular areas often less evident. 

On roots of poor quality the adults are brown or orange and the 
tubercular areas hardly perceptible to the naked eye. After weeks 
of egg production old adults become brown or purplish brown. In 
shape the adults while not engaged in egg laying are hemispherical 
or short oval, about equally rounded at either extremity, but while an 
egg is being passed the insect assumes a pyriform shape and the 
caudal end is much tapered and extended. 



Mature radicicole. 
Pi. IX, a, b, c. 

Color varying from pale green and pale yellow to deep purplish brown, de- 
pendent on character of food and age of individual ; shape hemispherical, 
short oval, pyriform while passing the ova ; body obscurely glabrous, often 
appearing to be coated on the dorsum with a very fine whitish powder; under 
side of abdomen paler than upper. Body about twice as long as wide, widest 
at middle of mesothorax ; highest at about cephalic third ; body flattening both 
cephalad and caudad from this point. Head with dusky central area ; eyes 
dark red, each composed of three circular facets, arranged in form of an equi- 
lateral triangle; antennae pale, not quite reaching posterior margin of head, 
composed of three joints, of which the two basal are subequal in length but 



68 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



joint 1 wider than joint 2 ; third joint about twice as long as the two basal 
combined and bearing a single oval sensorium near apex ; all three joints bearing 
hairs. Beak pale, base and tip shining and dusky, reaching to second or third 
abdominal tergite ; in specimens examined after they had transfixed the beak 
into the roots, this organ appears to be shorter, due to the telescoping of the 
sheath from the action of transfixing. 

Mesothorax largest segment of body, twice as long as prothorax, which is 
next largest ; mesothorax divided into two sections by transverse fold. Thoracic 
segments having median portions raised above lateral portions by means of 
two longitudinal curved folds. Metathorax very similar above to any of first 
five abdominal segments. Legs in pale specimens slightly darker than abdomen, 
coxse dusky. 

Sixth abdominal segment produced conically at each of its posterior angles 
and narrowed basally ; caudal segment twice as long as broad, bluntly rounded, 
with a small central emargination and fringed with a marginal row of pale 
weak hairs. 

The dorsum of the body bears six longitudinal rows of dusky circular tuber- 
cular areas, which under magnification appear as thickenings and roughen- 
ings of the epidermis, and each of these is surmounted by a single spine. 

Table XIX gives measurements of the adult radicicole. 

Table XIX. — Measurements of mature radicicole of the grape phylloxera, 

Walnut Creek, Calif. 



Individual No. 


Length 
of body. 


Maxi- 
mum 
width 
of body. 


Length 
of beak. 


Length 
of hind 
femur. 


Length 

of hind 

tibia. 


Length of antennal joints. 


Length 
of sen- 
sorium. 


1 


2 


3 


1 


Mm. 
0.854 


Mm. 
0.502 


Mm. 


Mm. 
0. 0795 
.0804 
.0839 
.0875 


Mm. 
0. 0786 
.0759 
.0748 
.0768 


Mm. 

0. 0223 
.0252 
.0260 
.0197 


Mm. 
0. 0251 
.0243 
.0230 
.0230 


Mm. 

0. 0661 
.0660 
.0673 
.0705 


Mm. 
0. 0224 






.0195 


2 


.878 
1.011 
.997 
.942 
.783 
.778 
.763 
.734 
.714 
.712 
.686 
.631 
.582 


.549 

.584 
.558 

.507 
.503 
.455 
.433 
.448 
.392 
.408 
.416 
.352 


0.281 


.0196 


3 


.0205 


4 






5 
















6 




7 
















8 
















9 
















10 
















11 
















12 
















13 
















14 































Measurements of beaks from nine adult hibernants were made 
March 18, 1915. Of these six, fixed in the root tissue, measured 0.27t5, 
0.243, 0.260, 0.252, 0.198, and 0.179 mm., respectively. The other 
three, not fixed since casting their last skin, measured 0.329, 0.317, 
and 0.299 mm., respectively. The basal joints of the rostrum are 
telescoped when the beak is thrust into the root. 

It is obvious from an inspection of Table XIX that the adult 
radicicoles vary greatly in size. This variation occurs whatever kind 
of food supply the phylloxeree are getting, although the average size 
is larger on good succulent food than on that of poorer quality. Indi- 
viduals 5 to 14 in Table XIX were all taken the same day (Mar. 18) 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



69 



from equally succulent pieces of severed roots. They show a con- 
siderable variation in dimensions, but, being hibernants, their aver- 
age dimensions are less than those of the summer generations under 
equally favorable food-supply conditions; for among the hibernant 
adults there always may be found a considerable number of small- 
sized individuals which evidently owe their physical inferiority to 
the vicissitudes of the long hibernation period. Radicicoles raised on 
fleshy and succulent nodosities attain an average size of about 1 by 
0.55 mm., those raised during the summer on other parts of the root 
system average slightly less, and the hibernant individuals average 
0.75 by 0.50 mm. 

Radicicole molts. — -The radicicole, in common with other forms of 
the phylloxera, invariably molts four times. 

In 1914 and 1915 records of molts were taken, and Tables XX and 
XXI indicate molting records of 20 individuals reared on severed 
roots in the laboratory cellar during the summer of 1914. 

Table XX. — Molting records of 20 radicicoles of the grape phylloxera, summer 

of 1914, Walnut Creek, Calif. 



Indi- 
vidual 
No. 


Date egg 
batched. 


Date of 
first 
molt. 


First 
instar. 


Date of 

second 

molt. 


Second 
instar. 


Date of 
third 
molt. 


Third 
instar. 


Date of 
fourth 
molt. 


Fourth 
instar. 


Total 
grow- 
ing 
period. 


Aver- 
age 
tem- 
pera- 
ture. 


1 
2 

3 
4 


July 22 
...do.. . 

July 23 
...do 


Aug. 6 
Aug. 7 
Aug. 6 
...do 


Days. 
15 
16 
14 
14 
14 
10 
10 
11 
11 
11 
12 
12 
11 
13 
14 
14 
15 
17 
19 


Aug. 9 

...do 

...do.... 


Days. 
3 
2 
3 


Aug. 11 
...do.... 
Aug. 13 


Days. 
2 
2 
4 


Aug. 14 

...do 

Aug. 16 


Days. 
3 
3 
3 


Days. 
23 
23 
24 


°F. 
68 
68 
68 


5 

6 

7 

8 

9 

10 

11 

12 

13 

14 


July 24 
July 25 

...do 

...do.... 

...do.... 

...do.... 

...do.... 

...do.... 

...do 

...do.... 

...do.... 

...do.... 

...do.... 

...do.... 

...do.... 

...do 


Aug. 7 
Aug. 4 

...do 

Aug. 5 

...do 

...do.... 
Aug. 6 

...do 

Aug. 5 
Aug. 7 
Aug. 8 

...do.... 
Aug. 9 
Aug. 11 
Aug. 13 


Aug. 9 
Aug. 6 

...do 

Aug. 8 

...do 

Aug. 9 
Aug. 8 

...do.... 

...do.... 
Aug. 10 

...do.... 

...do.... 
Aug. 13 
Aug. 14 
Aug. 20 


2 
2 
2 
3 
3 
4 
2 
2 
3 
3 
2 
2 
4 
3 
7 


Aug. 11 
Aug. 8 

...do 

Aug. 9 
Aug. 11 
Aug. 12 
Aug. 11 

...do 

Aug. 9 


2 
2 
2 
1 

3 
3 
3 
3 
1 


Aug. 14 
Aug. 9 
Aug. 11 

...do 

Aug. 13 
Aug. 14 
Aug. 13 
Aug. 14 
Aug. 11 


3 
1 
3 
2 
2 
2 
2 
3 
2 


21 
15 

17 
17 
19 

20 
19 
20 
17 


68 
68 
68 
68 
68 
68 
68 
68 
68 


15 
16 
17 
18 
19 
120 


Aug. 13 
Aug. 12 
Aug. 15 
Aug. 17 
Aug. 24 


3 
2 

2 
3 
4 


Aug. 15 
...do 

Aug. 18 
...do 

Aug. 28 


2 
3 

3 
1 

4 


21 
21 
24 

24 

34 


68 
68 
68 
68 
68 



























i Hibernant died unmolted Oct . 11. 
Table XXI. — Summary of Table XX. 



Average 
period. 



Maxi- 
mum 
period. 



Mini- 
mum 
period. 



First instar, 19 individuals 

Second instar, 18 individuals 

Third instar, 17 individuals 

Fourth instar, 17 individuals 

Developmental period, 17 individuals 



Days. 

13.3 

2.9 

2.5 

2.5 



Days. 



21.2 



34 



Days. 



10 
2 

1 
1 



15 



70 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



All the individuals utilized in this experiment were reared on 
severed pieces of roots in a petri dish under cellar conditions. In- 
dividuals 19 and 20 lived on a much poorer root than the others, and 
thus is explained the relatively slow growth (34 days) of the one 
and the early hibernation of the other. Individuals 4 and 14 moved 
away after their first and second molts, respectively. It will be 
observed from the summary that the average period of the first instar 
(13.3 days) is considerably longer than is that of the three succeed- 
ing instars combined (7.9 days). The comparative periods of the 
instars are about constant; that is, an individual with a short first 
instar will have short succeeding instars and one with a long first 
instar will have long succeeding instars. 

The records of Table XX were made in midsummer at a tempera- 
ture of 68° F. In the soil at such a time of the year the temperature 
is higher and the development of the phylloxera more rapid, while 
in spring and late fall the development is correspondingly slower. 
The developmental period of the hibernated larvae varies greatly, 
not so much from temperature as from other causes. There is an 
average period of two and one-half weeks from the commencement 
of feeding to the shedding of the first skin, and after that an average 
period of three weeks between the casting of the first skin and the 
shedding of the fourth, the second, third, and fourth instars occupy- 
ing an average space of a week each. As summer progresses the de- 
velopment of the radicicoles becomes accelerated, as may be observed 
from Table XXII. 



Table XXII. — Molting records of radicicoles of the grape phylloxera, March to 

July, 1915, Walnut Creek, Calif. 



Indi- 
vid- 
ual 
No. 


Date egg 
hatched. 


Date of 
first 
molt. 


First 
instar. 


Date of 
second 
molt. 


Sec- 
ond 
instar. 


Date of 
third 
molt. 


Third 
instar. 


Date of 
fourth 
molt. 


Fourth 
instar. 


Total 
grow- 
ing 
period. 


Aver- 
age 
tem- 
pera- 
ture. 


Gen- 
era- 
tion. 


1 

2 

3 

4 


Mar. 19 
...do.... 
...do.... 
...do.... 


Apr. 3 
Apr. 7 
Apr. 8 
Apr. 10 
May 27 
...do.... 
June 7' 
June 27 
June 30 
July 3 


Days. 
15 
19 
20 
22 
16 
16 
15 
11 
14 
17 


Apr. 10 
...do.... 
Apr. 13 
Apr. 17 
May 30 
...do.... 
June 10 
June 30 
July 2 
July 6 


Days. 
7 
3 
5 
7 
3 
3 
3 
3 
2 
3 


Apr. 16 
...do.... 
Apr. 18 
Apr. 21 
June 1 
...do.... 
June 13 
July 1 
July 4 
July 9 


Days. 
6 
6 
5 
4 
2 
2 
3 
1 
2 
3 


Apr." 22 
...do.... 
Apr. 23 
Apr. 25 
June 5 
...do.... 
June 16 
July 4 
July 9 
July 10 


Days. 
6 
6 
5 
4 
4 
4 
3 
3 
5 
1 


Days. 
34 
34 
35 
37 
25 
25 
24 
18 
23 
24 


°F. 
58.25 
58.25 
58.25 
58.25 
61 
61 
63 
65 
65 
65 


A. 
A. 
A. 
A. 


5. 

6 

7. 
8. 
9 


May 11 
...do.... 
May 23 
June 16 
...do.... 


B. 
B. 
B. 

c. 
c. 


10.... 


...do.... 


c. 



The individuals enumerated in Table XXII were reared under 
cellar conditions on equally succulent pieces of severed roots. Table 
XXII, both by itself and taken in conjunction with Tables XX and 
XXI, indicates the influence of temperature upon the development 
of the radicicole under equal food conditions. Under a temperature 
of 58.25° F. the period of growth averaged 35 days, under an aver- 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



71 



age of 61.75° F. this period was 24.75 days, under 65° F. it was 
almost 22 days, and under 68° F. it was lowered to 20.3 days 
(individual on unthrifty root disregarded). Under the lower tem- 
peratures all the instars are correspondingly longer than under the 
highest midsummer temperature, but the first instar is proportion- 
ately less lengthened than are those following it, a phenomenon 
that becomes quite apparent in the case of the hibernants, provided 
their first instar be considered in a restricted sense to cover only that 
period between the time when they commence feeding in spring and 
the date of the first molt. The hibernant feeds for two and one-half 
weeks before and for three weeks after its first molt, while in mid- 
summer the larva feeds for 13 days before and for 8 days after its 
first molt before it matures. 



MAXIMUM AND MINIMUM GENERATIONS YEARLY. 

In 1911 overwintered adult radicicoles matured at the end of 
April, throughout May and June, and as late as July 7. Eggs of 
the first generation were deposited from the end of April until 
October 1. From the earliest eggs there followed seven complete 
generations from hibernant to hibernant inside of the one year. No 
observations were taken of the hatching of the late eggs deposited 
by late first-generation phylloxerse in September, but in the light of 
contemporary observations on individuals of later generations there 
is no doubt that a certain percentage of these late eggs would have 
hatched into hibernants, thus giving a minimum of one generation 
per annum. In 1915, taking advantage of a hibernant which ma- 
tured exceptionally early in the spring, it was possible to secure 
eight complete generations within the year. Table XXIII records 
the development of these generations. 

Table XXIII. — Maximum series of generations of radicicoles of the grape 
phylloxera, reared under cellar conditions, Walnut Creek, Calif., 1915. 



Generation No. 


Date of egg 
deposition. 


Date of egg 
hatching. 


Date insect 
matured. 


Genera- 
tion 
cycle. 


Temper- 
ature 
(average). 


li 


—1914 

Feb. 26,1915 
Apr. 27,1915 
June 7, 1915 
July 5, 1915 
July 28,1915 
Aug. 23,1915 
Sept. 25, 1915 
Oct. 27,1915 


—,1914 

Mar. 19,1915 
May 11,1915 
June 16,1915 
July 14,1915 
Aug. 4, 1915 
Aug. 31,1915 
Oct. 7, 1915 
Nov. 10, 1915 


Feb. 26,1915 
Apr. 22,1915 
June 5, 1915 
July 4, 1915 
July 28,1915 
Aug. 23,1915 
Sept. 23, 1915 
Oct. 27,1915 
—,1916 


Days. 


°F. 


2 


55 
39 
27 
23 
26 
31 
32 


58.25 


3 


61.20 


4 


64.50 


5 


69.50 


6 „ 


68.50 


7 


67.00 


8 


62.50 


9 1 











1 Hibernant. 



In this experiment the food supplied to the phylloxerae was, as 
far as one could judge, of equal quality and very nourishing. The 
influence of temperature is noticeable. 



72 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

In observations with phylloxerse developing on living vines there 
were secured in a period of three years 13 generations, an average of a 
little over four generations a year, but had the earliest eggs of each 
generation been successfully utilized, and had it been possible to 
start the first of the three seasons with the earliest eggs procurable 
in the vineyards, there is no doubt that six, and possibly seven, gen- 
erations could have been developed each year. 

Considering that the hibernant generation occupies a period of 
half a year, it is apparent that if seven generations are to be pro- 
duced in a year, the other six must be passed in an average maximum 
of one month apiece. In summer phylloxerse have been reared from 
egg deposition to maturity in 21 days, but in April, May, and Oc- 
tober the cycle rarely falls below 35 days, so that in the six-month 
period, April 15 to October 15, the average maximum cycle is roughly 
30 days. Thus, in the vineyard, even on vines that move early in 
spring, it is probable that more than seven generations rarely take 
place in 12 months. The period, October 15 to April 15, best rep- 
resents the cycle of the wintering generation, although these dates 
are somewhat arbitrary. 

Under vineyard conditions it is always possible to find hibernant 
phylloxerse as late as the beginning of June. It is also possible 
to find insects going into hibernation as early as September 20. Since 
the mature radicicoles deposit eggs for periods exceeding three 
months, it can be seen readily that the latest eggs of a radicicole 
hibernant maturing in June may develop larvse which proceed to 
hibernate. A minimum of one generation a year thus may occur. 
Observations indicate that this minimum of one generation is not 
common, even on moribund vines with innutritious roots. 

WANDERING RADICICOLE LARVAE OR " WANDERERS." 

By the term " wanderers " are designated those forms ( almost all 
newly hatched larvse) which forsake the root on which they issued 
from the egg and seek to reach the surface of the soil or to pass 
through the soil itself, with the object of finding new food. Those 
that strive to reach the surface exhibit in their efforts a very marked 
positive phototropism. It would appear that their first movement 
is simply one of ascending the root and that as soon as they are 
brought into the focus of a ray of light they immediately make it 
their goal, and thus finally ascend to the surface. The initial wan- 
dering movement comes irrespective of light rays, but as soon as 
these rays are brought to bear the activity is very pronounced. The 
conclusion is that the production of individuals destined to wander 
is due to a combination of influences more than to any single influ- 
ence — the crowded condition of the phylloxerse in summer, the decay- 
ing of the roots, especially the fleshy surface rootlets, found on 



Bui. 903, U. S. Dept. of Agriculture. 



Plate XI 




The Grape Phylloxera in California. 

Phylloxera vitifollae: a, Nymph, dorsal view; ft, outline ventral view of same; c, enlarged 
sensorium on antennae; d, enlarged tubercle with spine; e , microscopic structural view of 
tubercle;/, hind leg; g, beak showing structure; h, middle leg; r, right antenna; /, left 
antenna. 



THE GRAPE PHYLLOXERA 1ST CALIFORNIA. 



73 



phylloxerated vines, the rising temperature, and the intrinsic vigor 
of the vine encouraging emigration. 

Apparently the young produced from the eggs deposited by over- 
wintered females do not become wanderers, but those of later gen- 
erations may, and many wandering larvae produced late in the au- 
tumn settle on roots and hibernate. 

Wandering larvae play an important part in the diffusion of phyl- 
loxera. 

THE NYMPH AND WINGED FORM. 

DEVELOPMENT. 

The individuals which are destined to become winged are termed 
in their third instar " prenymphs " and in their fourth instar 
" nymphs." They are produced from eggs deposited by adult radi- 
cicoles, and until after their second molt differ in nowise from the 
individuals destined to remain wingless; neither is there any dif- 
ference in the eggs from which the two types hatch. In their third 
instar the prenymphs (PL X, d, e, f) differ from the radicicoles of 
that instar in that the former have more elongate and narrower bod- 
ies and longer antennae and legs. The prenymphs are generally pale 
greenish yellow, and their appendages appear quite dusky in com- 
parison. Table XXIV gives measurements of four prenymphs. 



Table XXIV. 



-Measurements. of prenymphs of the grape phylloxera, Walnut 
Creek, Calif. 



Individual No. 1 


Length 
of body. 


Maxi- 
mum 
width 
of body. 


Length 
of beak. 


Length 
of hind 
femur. 


Length 

of hind 

tibia. 


Length of antennal joints. 


Length 
ofsen- 
sorium. 


1 


2 


3 


1 


Mm. 
0.805 


Mm. 
0.405 


Mm. 
0.357 


Mm. 

0. 0948 
.0939 
.0946 


Mm. 

0. 0821 
.0839 
.0713 


Mm. 

0. 0330 
.0321 
.0306 
.0306 


Mm. 

0. 0268 
.0277 
.0279 
.0279 


Mm. 

0. 0839 
.0889 
.0973 
.0919 


Mm. 
0. 0196 




.0193 


2 


.660 


.325 


.193 








3 


.541 
.555 


.300 
.284 


.186 








4 































1 Individual 1, just before molting into nymph; individuals 2 to 4, very shortly after molting into pre- 
nymphs. 

The prenymph molts into the nymph or pupa. The pupa is the 
longest of all forms of the insect and is easily discernible on the 
root by the presence of wing pads, even just after it has molted from 
the prenymphal form, and has a greenish color. Immediately after 
the skin is shed, these wing pads are yellow, but very quickly they 
become gray or blackish. During the first few days of the nymph al 
instar the insect is green or greenish yellow, and the compound eyes 
are indiscernible, but as it grows it lengthens, becomes constricted in 
the region of the metathorax, and turns orange, the mesothorax, how- 
ever, remaining paler than the rest of the body. The compound 



74 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



eyes show their red pigment and soon become prominent. Legs and 
antennae are relatively long, and the femora exceed the tibiae in 
length. At all times the rows of tubercular areas on the dorsum are 
well marked. During the nymphal instar the insect shows a very 
considerable growth; the newly molted individuals are quite flat, 
but full-grown nymphs are roughly cylindrical. 

DESCRIPTION OF STAGES. 



The nymph or pupa, full grown. 
PI. XI ; text fig. 9, p. 85. 

General color orange or orange yellow; anterior part of mesothorax and 
mesosternum whitish, or at least always noticeably paler than the rest of body. 
Antennae pale yellow, extended but little beyond anterior margin of prothorax. 
Compound eyes and ocelli dark red ; former composed of large number of facets. 
Head and abdomen bearing 4, thorax 6 longitudinal rows of dark tubercular 
areas (coarse roughening of epidermis), each surmounted by a spine; wing pads 
"dark gray, grayish black, or rarely jet black; legs pale yellow, often with a 
dusky cast ; abdomen with 7 visible segments, mesothorax apparently bisected by 
a transverse fold ; beak very pale yellow, reaching to posterior coxae. 

Measurements of 6 individuals are given in Table XXV. 

Table XXV. — Measurements of nymph of the grape phylloxera, Walnut 

Greek, Calif. 



Individual No. 1 


Length 
of body. 


Maxi- 
mum 
width 
of body. 


Length 
of beak. 


Length 
of hind 
femur. 


Length 

of hind 

tibia. 


Length of antennal joints. 


Length 
of sen- 
sorium. 


1 


2 


3 


1 


Mm. 
1.102 


Mm. 


Mm. 
0.3295 


Mm. 
0.1500 
.1464 
.1419 
.1438 
.1089 


Mm. 

0. 1366 
.1384 
.1321 
.1304 
.1071 


Mm. 


Mm. 

0. 0402 
.0350 
.0331 
.0332 
.0339 
.0295 


Mm. 

0. 1536 
.1545 
.1455 
.1455 
.1179 
. 1184 


Mm. 
0. 0223 






0. 0339 


.0224 


2 j. 


.889 




.3600 


.0230 








.0254 


3 


.957 


.507 


.3339 


.0321 
.0304 


.0223 




.0232 


4 


.851 

.798 

.725 

1.121 

1.197 












5 


.511 


.2695 


.1389 


.1252 


.0315 


.0309 


.1577 


.0198 


6 




7 


.558 
.569 
















8 

































1 Individuals 1,7, and 8 at end of stage; 4,5, and 6 at beginning of stage; 2 and 3 about middle of stage 

Newly molted nymphs average about 0.78 mm. in length and ma- 
ture nymphs about 1.1 mm. The nymphs are always more active 
than the immature wingless forms, wandering larvae excepted. Their 
eyes are well developed, as in the winged insect, and they have the 
ocelli found in that form. The third joint of the antennae bears a 
single sensorium corresponding to the apical one of the migrant, and 
as the last molt approaches the migrant antennae show through the 
nymphal skin, and thus the nymphal antennae appear to bear two 
sensoria. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 75 

The adult instar of the winged form shows what is probably the 
most highly developed form structurally of the phylloxera. The 
winged insect is, on the average, slightly shorter than the full- 
grown nymph. The antennae are longer than those of the previous 
instar and bear two sensoria of about equal size. The comparatively 
large wings are weakly veined but necessitate strong muscles in the 
interior of the thorax. The legs are quite long and the tibise exceed 
the femora in length. As the migrant sheds the nymphal skin, push- 
ing it back and moving about its appendages, the wing pads appear 
as little white rolls; the mesothorax is shining green, the head and 
abdomen bright orange. The wings unroll as the skin is being passed 
off the abdomen. As soon as it is entirely shed the insect moves off 
and then pauses while the wings assume their final shape and posi- 
tion, but remain whitish, hyaline, and limp. Soon, however, the 
wings dry and the thorax hardens and darkens until it is almost 
black. The head, prothorax, and abdomen remain orange, the head 
with a grayish luster. The molting process occupies about 50 
minutes. 

The adult winged form. 

PI. VIII, a~e. 

General color orange or yellowish brown or gamboge yellow; head a little 
dusky on the anterior half, especially the cephalic margin (front) ; ocelli dark 
red ; eyes brighter red than ocelli, compounded of many facets ; ocular tubercle 
small ; antennae with three joints, not quite reaching the anterior margin of 
the mesothorax, pale yellow, with apical fourth of joint 3 dusky gray; third 
joint much the longest, considerably over twice as long as first two combined, 
somewhat constricted beyond the basal sensorium and at extreme base ; posterior 
half of head, prothorax, and abdomen orange, yellowish brown, or gamboge. 

Thoracic lobes, scutellar lobes, scutellum, and mesosternum dark gray or 
blackish; legs pale yellow,' tarsi duskier; wing insertions, stigma, and veins 
gray (at first greenish) ; stigma equal in length to about one-fourth of wing. 

First discoidal arising from subcosta not far from basal angle of stigma, 
stout, not attaining the wing margin by a space equal to one-fifth its length; 
second discoidal faint, arising from the first vein or discoidal a little before 
its center and almost reaching the wing margin at a point a little nearer to 
the apex of the third discoidal than to that of the first; third discoidal faint, 
arising from first vein close to its base and continuing with a double shallow 
curve almost to the wing apex (the basal half of this vein generally obsolete). 
Lower wings with the costal vein running parallel to the anterior margin 
for its whole length ; cauda bluntly rounded, bearing a fringe of hairs ; beak 
slender, pale yellow, and almost reaching to second coxse; two longitudinal 
oval sensoria on the third antennal joint ; basal sensorium situated at basal 
third of joint, apical sensorium close to apex of joint. Wings borne hori- 
zontally, apparently the positions interchangeable, the right pair sometimes over- 
lapping the left and vice versa. Abdomen widest at second and third abdominal 
segments, where it is wider than the thorax, and about as -long as head and 
thorax combined. Body about as high as wide, not at all flat. 

Table XXVI gives the measurements from 8 individuals. 



76 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



Table XXVI. — Measurements of the winged migrant of the grape phylloxera, 

Walnut Creek, Calif. 





1 


2 


3 


4 


5 


6 


7 


8 


Length 


Mm. 

1.101 
.428 
.333 


Mm. 


Mm. 


Mm. 


Mm. 

0.906 

.317 

.309 

.0320 
.0366 
.1741 

.0536 

.0214 

.0250 
.1848 
.2062 
.229 


Mm. 


Mm. 


Mm. 
0.900 


Width (abd. see:. 3) 












.390 


Width (thorax) 














Antennal joints, length: 

1 


0. 0384 
.0402 
.1902 

.0562 

.0268 

.0286 
.1901 
.2179 


0.0375 
.0393 
.1809 

.0634 

.0304 

.0269 
.1802 
.2250 


0. 0321 
.0304 
.1777 

.0241 

.1500 
.1643 


0.0393 
.0384 
.1946 

.0589 

.0304 

.0277 






2 




0.063 
.0275 
.0297 


.033 


3 




.207 


Antennal joint 3, base to apex of basal 
sensorium 






Antennal joint 3, length of basal sen- 
sorium 1 






Antennal joint 3, length of apical sen- 
sorium 






Hind femur, length 






Hind tibia, length 










Beak, length 










Wing expanse 












2.73 





















The prenymphal instar is passed in three or four days, in the same 
time in which the corresponding instar of the wingless radicicole is 
passed. The nymphal instar, however, is relatively longer than the 
corresponding instar in the wingless form, and it is because of this 
fact that the migrant takes longer to mature than does the contempo- 
raneous wingless radicicole. The nymphal or pupal instar occupies 
from 5 to 12 days, the average being about 8 days. 

The nymphs take more food than does the corresponding wingless 
form, and after they have left a nodosity or tuberosity upon which 
they have been feeding, the lesion rapidly decays unless other in- 
dividuals are settled upon it. The nymphs do not usually move 
much during their period of growth, but if disturbed they move 
quickly and display a negative phototropism when suddenly exposed 
to light. The newly molted nymphs, however, often wander about 
with apparent aimlessness. The full-grown nymphs just before 
molting ascend the roots, seeking the surface, and transform on the 
trunk or else find their way along the root until they come to a crack 
in the soil, and crawling up the sides of the crack transform near the 
surface. In glass sections cages, wherein the glass plates did not fit 
very tightly to the soil, the nymphs were found sometimes crawling 
up to within 2 or 3 inches of the surface and sometimes transforming 
close by the roots as much as 17 inches below the soil surface, the 
resultant winged aphids being compelled to find their way to the 
surface. It was concluded that owing to the loosely fitted glass 
plates of the section cages, which allowed abnormal light to penetrate 
below the surface of the soil, the nymphs did not wait to ascend to- 
ward the surface, but transformed below, their transformation being 
governed by the strength of the light rays to which they were sub- 
jected. It may be said that these section cages measured 9 by 24 
inches, outside measurement, and allowed of a thickness of half an 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 77 

inch of soil, which was a silty loam mixed with heavier clay loam. 
In some half-darkened cages, containing potted vines, the nymphs 
were observed to ascend to the level of the soil surface to transform. 
On the other hand, occasional nymphs have been found to transform 
on the roots as much as several feet underground, and many of the 
resultant migrants failed to reach the surface of the soil. 

HABITS OF WINGED MIGRANTS. 

Occasionally it was noticed in the jars that migrants would thrust 
their beaks into the roots and appear to feed. While engaged thus 
they lower the head so as to allow the beak to penetrate the tissues 
of the root. This organ appears to issue from the mesosternum, 
because of the curvature of the sheath. The femora are kept hori- 
zontal, and the antennae are usually in motion. While the insect is 
walking the antennae are in motion. The migrants, so far as has 
been noted, never feed after they issue from the soil. At all times 
they exhibit strong positive phototropism. When placed in a room 
they seek to crawl toward windows, and their activity is greatly 
increased when placed in the direct sunlight. If placed in a petri 
dish in the sunlight, they travel very fast and often take to flight, 
and are capable of keeping up a walking gait for hours. If the 
surface upon which they are standing becomes heated, they quickly 
die. If a vine leaf or other shade-giving object is placed in the dish, 
the phylloxerae will finally settle on the shady side of the object. 
In the vineyard most of the winged phylloxerae were observed to 
issue from the soil by creeping up the stumps of the vine. On arriv- 
ing at the surface many of them passed to the soil and crawled 
around aimlessly. Others crawled up the vine, and when they 
reached a point of vantage, such as the end of a cane, they spread, 
and vibrated their wings, as though inviting the wind to bear them 
off. Finally they launched themselves into the air and if they struck 
a wind current were borne off. Often after spreading their wings 
once or twice they turned about and crawled down the stalk, and 
frequently when they launched themselves into the air no current of 
wind caught them, and they half fell and half flew to the ground 
in an oblique direction, but at other times they flew off strongly 
without the aid of the wind. The migrants are capable of traveling 
by flight and with the wind, as is evidenced by the experiments con- 
ducted with sticky papers. (See Diffusion of phylloxera, p. 100.) 
They have been taken on such papers at least 80 feet from the near- 
est infested vine, and undoubtedly they may travel much farther. 

In order to ascertain whether the migrants returned to the soil by 
crawling down the stem of the vine, 26 migrants were placed on the 
upper foliage of a small American vine (9 inches in height), on 



78 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

August IT, 1914. Around the base of the vine stem were placed 
sticky papers, and the stem was encircled with glue. The vine was 
kept indoors and was not exposed to wind currents. Six hours after 
the phylloxera? were placed on the leaves, eight individuals were 
caught on the paper. After 24 hours, IT winged phylloxera? were 
on the paper and 3 dead on the leaves, none having been caught in 
the circle of glue on the stem. Thus the phylloxera? had either flown 
or dropped down and none had descended the full length of the stalk. 
Since none of the individuals on the papers were over 4 inches from 
the stem it would appear that they dropped rather than flew from 
the vine. 

On August 22, 1914, 34 winged phylloxera? were placed on the 
foliage of a riparia vine, 12 inches in height. This vine was potted 
and sunk in the soil and exposed to field conditions. Around the base 
an area of sticky paper 30 by 36 inches was laid. After two days an 
examination of the paper showed on the leeward side eight winged 
phylloxera?, occurring 16J, 16J, 16, 16, 12, 10, 6, and 1J inches, respec- 
tively, from the stem, and one winged phylloxera on the windward 
side 2 inches from the stem. The remaining 25 were not recovered, 
and probably flew off or were blown beyond the paper. The location 
in which this experiment took place was subjected to wind that blew 
from one direction only. It is obvious that the wind was a factor in 
the distribution of these phylloxera?. 

In the observations on the flying of the migrants it was found 
that individuals would fly both in the sunlight and in the shade, 
that very frequently they refused to launch themselves even in 
bright sunlight and in all varieties of wind currents, and that they 
appeared to take no definite direction in launching themselves. As 
a general rule, the winged forms fly more abundantly in the sun- 
shine than in the shade, and they are the more active the hotter and 
drier are the conditions of their environment. 

PRODUCTION AND RELATIVE ABUNDANCE OF MIGRANTS. 

In 1911, in the course of rearing experiments conducted in the 
laboratory cellar, the first winged forms were secured on August 2. 
These had been raised on a heavily infested piece of vinifera root 
and were part of the third generation of that year. In five localities 
in central California nymphs were collected in vineyards from 
August 3 to 19 and, judging from observations made in years fol- 
lowing, it is possible that nymphs had been developed earlier in 
that season. In the laboratory the production of migrants proceeded 
until the end of November, but in the latter half of October and in 
November only a few developed. 

In 1912 no record was made of the earliest appearance of nymphs 
and migrants, but they were found abundantly on } r oung potted 



THE GKAPE PHYLLOXERA IN CALIFORNIA. 79 

vines (mostly resistants and American nonresistants) during Sep- 
tember and October, and some were reared in the cellar during 
August. 

In 1913 the first nymph was observed, July 9, on the root of an 
American vine, and at about the same time others appeared on 
young resistant hybrids in pots. On the severed pieces of vinifera 
roots kept in jars in the cellar nymphs occurred as early as July 12, 
and on July IT the first migrants appeared. This was the first year 
in which experiments were conducted with living vines in cages, 
and on these the earliest nymphs and migrants were reared on 
July 20 and 28, respectively. In the experimental vineyard (Zin- 
fandel) migrants were first collected about August 1, but some 
nymphs were found on July 25 in a vineyard at Napa, Calif. In 
general, migrants continued to develop until November, but after 
the middle of October their production was scanty, and in the vine- 
yard very few were found later than September. 

In 1914 nymphs were first observed on June 16, both in the ex- 
perimental vineyard at Walnut Creek and on roots kept in the 
cellar. On June 18 a migrant was reared from a nymph collected 
in the vineyard two days previously. On the roots of the vines 
growing in cages nymphs were reared June 23. Throughout July 
and August nymphs and migrants were abundant in the Zinfandel 
vineyard. In September the numbers fell off rapidly and none were 
found in October. In infested vines in pots migrants were secured 
in considerable numbers throughout August and September, but 
were much more scarce in October. 

In 1915, in the material reared under cellar conditions, the first 
nymph was observed on June 14. The day following, a nymph oc- 
curred on the root of a young vine planted in a section cage. In the 
cages containing living vines, the first nymph was reared June 23, 
and in the experimental Zinfandel vineyard, nymphs were collected 
June 22 and evidently occurred as early as June 15. In the vineyard 
the production of migrants continued until the end of September, 
and was abundant from July 15 to the end of August. In the ma- 
terial in the cellar jars, abundant migrants were secured throughout 
the months of July, August, and September, and the production con- 
tinued until November 8. 

In summing up, it may be said that in California the period in 
which migrants are developed in vineyards extends from the middle 
of June until the end of October ; that these forms appear in great- 
est abundance from the middle of July to the middle of September 
(the hottest time of the year) ; and that the production is very 
limited in June and October. In small vines in pots, especially if 
consistent irrigation is practiced, the October production of migrants 



80 BULLETIN 903, U. S. DEPARTMENT OE AGRICULTURE. 

was frequently large. In the case of pieces of vine roots kept in a 
cellar, abnormal conditions of food, temperature, and humidity fre- 
quently arose. 

The conditions which affect the relative abundance of migrants 
are the following : Variety of vine, vigor of vine, humidity, tempera- 
ture, condition of roots, character of soil. 

Resistant and certain American nonresistant vines normally bear 
the greatest proportion of migrants. These vines are the descendants 
of the wild grapevines which formed, and still form, the natural 
food plant of the phylloxera, and which were immune from serious 
injury by reason of the fact that there was produced each year a large 
percentage of migrants, while few or no wingless forms persisted on 
the vines after the winged forms had departed. The wingless 
radicicole forms during the summer fed only upon the terminal 
rootlets, and when these decayed the vine was easily able to replace 
them without suffering injury of any consequence. The resistant 
vines of to-day, except in instances in which the roots have been 
supplied with poor or insufficient soil, as is noted below, do not sup- 
port heavy and continued infestations of wingless phylloxera, and 
almost all the phylloxeras born in summer and autumn develop 
wings and become migrants. It may be said here that experimenting 
with resistant vines grown in pots with soil unchanged for over a 
year is apt to give misleading results, for as the soil becomes poorer 
and insufficient for the increasing root system of the vine, fibrous 
rootlets become scarce, and an abnormal infestation of wingless 
phylloxeras and a diminishing production of migrant phylloxera; en- 
sue, thus approaching the conditions normally found on vinif era vines. 
On vinifera vines and on many American nonresistants, such as 
Isabella, Catawba, and Champion, the production of winged migrants 
is never proportionately as large as that which occurs on resistants. 
Well-nourished resistant vines have been observed to rid themselves 
entirely of the phylloxeras, the insects all departing as winged forms, 
and in all cases under normal conditions, if any wingless forms 
remain after the winged forms have all left, the number is very 
small. On vinifera vines the total nymphal production has been 
found to be over 33 per cent of the whole in season, although three- 
fourths of the individuals produced on fleshy surface rootlets and on 
nodosities have been observed to develop into migrants, and on suc- 
culent pieces of severed root cuttings as large a proportion has been 
reared. 

In the vineyard the larger roots were rarely found to produce a 
number of migrants in excess of 25 per cent of the whole number of 
phylloxeras simultaneously developed, and under unfavorable condi- 
tions extremely few and sometimes no migrants were produced. 



THE GKAPE PHYLLOXERA IN CALIFORNIA. 81 

Under average conditions the proportion on the larger roots was 
between 5 and 10 per cent. Regarding the American vines of non- 
resistant type, a considerable diversity in the production of nymphs 
has been observed. On some, like Moore's Early, this production 
may be proportionately very large, while on others, like Isabella and 
Catawba, it may be smaller than on viniferse, as occurred in the ex- 
periments in caged and potted vines. Vines like Agawam, Lenoir, 
and Delaware, vinifera crosses, bore about the same proportion of 
nymphs as the viniferse, but among the labrusca types (Isabella, 
Moore's Early, Concord, Champion) there was considerable variation. 

On resistant vines, the nymphs are developed on the nodosities, but 
on viniferse and American vines of nonresistant type they are also 
produced on other portions of the root system. On phylloxeratecl 
viniferse, the most abundant production of nymphs occurs on the 
fleshy and fibrous surface rootlets frequently observable in the 
vineyard. These rootlets are sent out in May and June, and often 
become grossly infested with phylloxerse in June and July. Toward 
the end of July, they decay or dry out, and after that nymphs are 
produced only on the larger roots and on nodosities deeper in the soil. 
On the larger roots relatively few nymphs are produced before August 
or after September. 

Among viniferse the more vigorous vines produce the greater pro- 
portionate numbers of winged forms. Badly stunted vines showing 
several years of phylloxeration produce comparatively few, while 
the recently attacked vines around the periphery of " spots " produce 
large quantities. Viniferse vines in pots produce great numbers the 
first year of infestation, but if the soil is unchanged in the second 
and third years, as the vines become weakened, they produce fewer 
winged forms. 

As far as has been observed, all varieties of viniferse produce the 
same proportion of migrants. 

It has been observed frequently that a humid environment stimu- 
lates the production of migrants and a dry one precludes it. This has 
been especially noticeable in the cases of young vines in pots and of 
the severed roots kept under cellar conditions. The late appear- 
ance of the migrants in the experimental vineyard in 1913 as com- 
pared with those of 1914 and 1915 was perhaps due to lack of moisture 
in the soil in summer. The spring of 1913 was exceptionally dry, 
and the ground became very dry by June, whereas in the two years 
following, moisture was conserved in the top soil until July. The 
total migrant development of 1913, however, although at first re- 
tarded, was finally just about as large as those of the succeeding 
years. To hold the severed pieces of roots, glass jars and dishes were 
used in the cellar, and it was found that in the summer and fall 

1900°— 21 6 



82 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

a la} 7 er of wet sand placed in the bottom of the jar was conducive 
to the production of migrants. When moisture was applied peri- 
odically to filter papers, the production of migrants was greater 
the more frequent the applications. 

What effect, if any, temperature has upon the production of 
migrants can not be shown except that they are produced during the 
hottest months of the year. Contrasting the hot summer of 1913 
with the cooler one of 1914, it was found that the production was 
about equal each year. 

Migrants are produced in greater numbers in soils which retain 
moisture than in those which dry out rapidly. Otherwise no further 
influence traceable to soil conditions has been noticed. Although the 
general behavior of phylloxera differs considerably in relation to 
different types of soil, as between these different types the production 
of migrants does not appear to change. 

In the season 1914, 12 vinifera vines were growing in cages. These 
were inoculated in the spring, and six of 'them later treated through- 
out the summer and autumn with fertilizers applied in liquid form 
periodically. These fertilizers — nitrogen, potash, phosphoric acid, 
and magnesium — were combined in a normal fertilizer and also 
used in combinations in which one element was in marked excess. 
The fertilized vines produced noticeably larger nymphal infestations. 
In 1915 other potted vines were treated likewise, except that all 
the fertilizer was mixed with the soil at the time of planting, and 
the vines were not inoculated until a month later. In this series the 
number of nymphs was no greater or less on the fertilized vines than 
on the unfertilized. 

Migrants formed part of radicicole generations 2 to 5, those of the 
third generation being the most abundant. It was never observed 
that any of the first generation (direct progeny of the hibernants) 
became winged. 

NYMPHICALS OR INTERMEDIATE FORMS. 

The insects of the nymphical type are intermediate in form between 
the winged migrant and the wingless radicicole. In their adult 
stage they vary largely. Grassi (11) has figured and described sev- 
eral individuals which represent stages in the variation. His speci- 
mens varied from a type which differed only from the radicicole in 
the possession of two or three extra eye facets and in longer append- 
ages to one which superficially resembled a nymph in that it had well- 
developed compound eyes and noticeable wing pads. This last type, 
however, upon close examination, differed from the nymph as follows : 
(l)The antennae (fig. 8; compare with fig. 9, antenna of nymph) 
frequently bore two sensoria, as in the winged insect, but the basal 
sensorium was less developed than in that form: (2) the wing pads 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 83 

were not hard and straight and parallel to the sides of the body, but 
bulged out and appeared rolled up and were soft, also sometimes con- 
taining the sensory organs peculiar to the wing of the winged forms ; 
(3) there were no wing muscles in the interior of the thorax; and (4) 
the structure of the vaginal segment of the abdomen was more devel- 
oped than in the nymph. From this it appeared that this type of 
nymphical was more comparable to the winged insect notwithstand- 
ing its superficial resemblance to the nymph, and this conclusion 
would be the more obvious when it is considered that the nymphical 
is an adult insect of the fifth stage. 

In Italy the intermediates are said to be quite abundant among the 
nymphs in the season of the year (July to October) when the latter 
are being produced on the vines. They were found to be especially 
abundant on vines of the American type but also not uncommon on 
viniferae. 

In California, in the year (1915) in which were carried on re- 
searches upon the intermediate forms, there was a very small avail- 
able supply of infested American vines, and the observations were 
confined chiefly to viniferse. On the American vines such as were 
examined one nymphical was found. 

In looking over a series of slides made in 1914, a single nymphical 
was recognized; the year following, during the nymphal season (June 
to November), frequent examinations were made on vinifera vines, 
and in all 15 intermediates were secured from these. The individual 
from the American vine (Wyoming Eed) and nine of those on vinif- 
erae were recognized through the medium of mounting large numbers 
of insects and later examining them through the microscope. The 
remaining six were discovered on the roots through the use of a 
binocular microscope, and all of them had rudimentary wing pads, so 
that it is likely that others of the type lacking these pads were ob- 
served but not recognized as intermediates. 

In the two years covering the investigation a total of 17 inter- 
mediates came under observation. None of these was found earlier 
in the year than the middle of September, and 12 were collected or 
observed between September 14 and 27, 1915, and 1 on September 10, 
1914. Of the 4 remaining, 1 was observed on a piece of root October 
14, 1915, and 3 others October 27, 1915, 1 of which was in the fourth 
stage and matured November 1. These 17 individuals differed 
greatly one from another and represented all the types discussed by 
Grassi and Foa. The types intergrade, and, in fact, no two of the 
examples were alike. For the sake of comparison, they may be 
divided into three arbitrary groups: (1) Those without vestige of 
wing pads; (2) those with small buttonlike wing pads not visible 
from above; (3) those with larger wing pads protruding (as in the 
nymphs, fig. 9) beyond the lateral margin of the body and there- 



84 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 




Fig. 



6. — Phylloxera vitifoliae: Intermediate of 
type 2, ventral view. Much enlarged. 



fore visible from above. In group 1 were two individuals collected 
on young vinifera vines. One of them greatly resembled an adult 

wingless radicicole, but be- 
sides the larval eyes it had 
two to three extra facets, and 
the antennae and legs were 
longer than in the radicicole. 
The other was slender, re- 
sembling a prenymph in 
shape, and had about six ex- 
tra eye facets, and one an- 
tenna showed two sensoria. 
Group 2 (fig. 6) had six rep- 
resentatives, all with small to 
very small rudimentary wing 
pads invisible from above. 
In all cases the antennae (fig. 
8) and legs were long, and 
one insect had two sensoria 
on antennal segment III. In shape the individuals resembled wing- 
less radicicoles. One specimen (from Wyoming Red) had no extra 
eye facets, and the others from young vinif erae had a varying number, 
usually 10, although one had about 15. The remaining 9 individuals 
came under group 3 (fig. 7), 
and, because of their more pro- 
nounced nymphlike characters, 
these are more easily observed 
in life upon roots than are 
those of the other two groups, 
and 4 of the 6 individuals rec- 
ognized alive on roots were of 
this type. 

It is probable, judging from 
random collections, that the 
insects of groups 2 and 3 are 
about equally abundant and 
each somewhat more so than 
those of group 1. All the in- 
dividuals of group 3 had rudi- 
mentary wing pads, in many 
cases almost as large as the wing 
pads of the nymphs. They bulged out from the sides of the insects, 
and were soft and appeared coiled (fig. 7) or curled. The com- 
pound eyes were well developed, there being from 06 to 100 per cent 
as many facets as in the nymphal eyes. In some cases the larval 




10 




Fig. 7. — Phylloxera vitifoliae: Intermediate of 

type 3, ventral view, much enlarged; an- 
tenna at light, more enlarged. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



85 




Fig. 8.- 



Phylloxera vitifoliae: Types of antennae of 
intermediates. Greatly enlarged. 



eyes were absent, and in no case were ocelli discernible. In most in- 
dividuals there were two sensoria on the last antennal joint, and in 
one antenna there were two small basal sensoria and the usual 
apical sensorium, making 
three in all. The basal sen- 
soria were not in any case 
as large as those of the 
winged migrant. The an- 
tennae and legs were about 
as long as those of the 
nymph, noticeably longer 
on the average than those of 
the individuals of group 2, 
which in turn were longer 
than those of the two indi- 
viduals of group l. 10 It would appear, therefore, that greater devel- 
opment of wing pads and compound eyes is complemented with a 
lengthening of legs and antennas and a tendency to bear the extra 
sensorium of the winged forms. The femora exceed the tibiae in 
length. 

There is among the intermediates a tendency toward asymmetry. 
This was remarked in Italy and has also appeared in California. 

One eye may have more facets than the 
other ; the lengths of antennas and legs 
may differ in individuals, those of one 
side being longer than their counter- 
parts, and one antenna may possess 
more sensoria than the other. 

In two instances the fourth stage of 
intermediates was observed in Califor- 
nia. In one case an individual of group 
3 molted from what appeared, under 
the lenses of the binocular microscope, 
to be a true nymph. In the other case 
an example of the same group molted 
from an insect which itself resem- 
bled a nymphical; in fact, after the 
molt the individual did not appear 
to have changed its structure at all. 
In both fourth and fifth instars the 
wing pads were large and " fleshy." 
From three individuals, all of group 3, eggs were obtained. These 
eggs could not be differentiated from eggs laid by wingless radici- 
coles. One nymphical deposited two eggs, which were lost. An 

10 The insect depicted in figure 7 is considerably less enlarged than that represented in 
figure 6. 




Fig. 9. — Phylloxera vitifoliae: Nymph 
and antenna of newly molted in- 
sect, for comparison with interme- 
diates. 



86 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

other deposited two eggs, on September 28 and 29, respectively. 
These hatched in 11 days, the resultant larvae obviously being 
radicicoles but surviving only a few days. The third individual 
matured November 1, and between this date and November 10 it 
deposited 10 eggs. After this it became weak, and on November 16 
was mounted on a slide. The eggs were exactly similar to those laid 
by wingless radicicoles, and two of them measured, respectively, 
0.310 by 0.166 mm. and 0.297 by 0.168 mm. Seven eggs were trans- 
ferred for observation to another root, and three eggs hatched in 
from 14 to 16 days, the resultant larvae settling down for hibernation. 
One of these soon died, but the other two passed the winter in due 
form, and matured in April, 1916. Both of them were typical 
radicicoles and subsequently deposited many eggs. 

In Italy Grassi and his assistants found that the great majority 
of the intermediates were parthenogenetic, but one individual was 
found to contain a sexed egg. In discussing the phenomenon of the 
intermediates, they gave it as their opinion that the parthenogenetic 
individuals were those which up to their third stage were destined 
to become radicicoles, but in that stage changed their development 
to that of winged migrants, while the character of their eggs had 
been already fixed before the change and so remained parthenogene- 
tic. In the case of sexuparous intermediates the change was made 
in the reverse direction, the larvae at first being destined to become 
migrants and, therefore, when they matured as nymphicals they 
deposited sexed eggs. 

In California the recorded eggs laid by nymphicals were all par- 
thenogenetic, but the possibility of some of such eggs being sexual is 
not entirely excluded, in the writers' opinion. 

The nymphicals do not leave the roots in the manner of the 
winged insects, and therefore deposit their ova on the roots. In the 
case of sexuparous nymphicals, the sexes and winter egg would 
presumably develop underground. Whether in California such a 
development occurs or not can not be stated from our present knowl- 
edge, but in view of the fact that for many years the leaf galls have 
been unknown, it appears certain that such a cycle proceeds no 
further than the winter egg. 

DEPOSITION OF THE SEXUAL EGGS. 

The migrants deposit eggs (PI. VIII, /, h, i) which are of two 
kinds, viz, male and female, and from these eggs issue the true sexual 
aphids. Sexual eggs have never been found by the writers in the 
vineyard, either on viniferae or on resistant vines, although a large 
number of vines have been examined. In laboratory experiments a 
large number of sexed eggs have been produced. Considerable dis- 
cussion has taken place among European writers as to the normal 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



87 



location of the sexed eggs. Taking the sum of these discussions, 
it appears that they are placed on the underside of the leaves and 
more abundantly in the bark, generally between the year-old layer 
and that of the current year, and are fastened to the inner side of 
the former. Occasionally eggs are found at the base of canes where 
the new wood joins the old, and rarely on the vine supports (stakes). 
They are laid on both viniferse and resistant vines, but preferably on 
the latter. 

Observations were conducted in small cages, and in a few instances 
on living vines in pots. In the latter instances eggs were found laid 
on both the foliage and bark. Many different kinds of cages were 
used and experiments with different degrees of light, moisture, and 
temperature were conducted. Vine leaves and pieces of bark were 
inclosed in the cages. As a rule, the migrants, though primarily 
attracted to light, deposited their eggs in semidarkness. They laid 
them on the leaves and more rarely on pieces of bark offered, but 
often also on the sides, lid, and floor of the cages and in cracks. In 
1911 the observations tabulated in Table XXVII occurred. 

Table XXVII. — Sexual production of the grape phylloxera, Walnut Creek, 

Calif., 1911. 



Number 
of mi- 
grants. 



25 
52 
65 

SO 

25 
36 
30 
83 



1 
? 

69 



30 



45 
103 



50 
40 



Date and location of migrants. 



Aug. 4-6: Riparia vine in pot. . . 
Aug. 7-8: Vinifera vine in pot . . 
Aug. 10-12: Riparia vine in pot. 



Aug. 13, 14: Vinifera vine in pot. 



Aug. 15: Riparia vine in pot 

Aug. 16: Riparia vine in pot 

Aug. 17: Glass tube in drawer 

Aug. 18, 19: Riparia leaves in petri dish 



Aug. 19: Leaves in petri dish 

Aug. 23: Leaves in petri dish 

Aug. 24: Riparia leaves in laboratory . 



Aug. 25, 26: Riparia leaves in petri dish. 



Aug. 25, 28, 29: Riparia leaves in petri dish. 
Sept. 2-17: Vinifera vine in pot 



Sept. 19-23: Riparia vine in pot. 
Sept. 25-29: Riparia vine in pot. 



Number 
of sexual 
eggs de- 
posited. 1 



16 



IS 

2 
1 

2 
5 

7 
5 

12 
1 
7 
1 
1 
1 
8 
1 
1 
6 
1 
7 

30 



Date of 
deposi- 
tion. 



Aug. 9 

Aug!"i6 

Aug. 15 
Aug. 20 

...do 

...do 



Aug. 21 
Aug. 22 
Aug. 23 
Aug. 19 
Aug. 23 
Aug. 25 
Aug. 26 
Aug. 27 
Aug. 28 
Aug. 29 
Aug. 27 
Aug. 28 
Aug. 30 
Sept. 3 
Sept. 25 



Sept. 29 



Date of 
maturing 
of sexes. 



Aug. 26 
Aug. 28 
Aug. 30 



Sept. 6 



Aug. 30 
Sept. 2 



Oct. 4 
Oct. 5 
Oct. 6 



Number 
of sexes 
ma- 
tured. 2 



1 Thirteen female and three male eggs. 

2 All maturing sexuals were females. 

Table XXV 'III. —Summary of Table XXVII. 



Number of migrants 

Number of sexual eggs deposited. 
Number of sexual eggs hatched.. 



734 

171 

13 



88 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

Individual egg deposition by migrants, recorded for 5 individuals, 
was as follows : 3, 2, 1, 4, and 3 ; average, 2.6. Obviously the great 
majority of migrants died without depositing eggs. The eggs above 
recorded were laid in from 2 to 9 days, the majority in from 3 to 5 
days, after the migrants emerged from the nymphal skin. The great 
maj ority of the migrants did not live more than 3 days after casting 
their final molt, confinement evidently having caused premature 
death. 

From 100 migrants produced August 15, 1912, and placed on a 
small vine August 20, a single egg, which failed to develop, was 
deposited August 24. 

In 1913 different types of cages were utilized in an effort to induce 
a larger percentage of eggs and mature sexuals. The results were 
not encouraging. From July 17 to October IT migrants were placed 
in the cages. During that time in some 60 experiments, 317 mi- 
grants were used, 99 sexual eggs were secured, and 7 sexed. phylloxeras 
(all females) matured. The migrants in no case lived more than 
6 days, the majority only 3 days, and quite a number did not move 
their position after having been placed in the cages. In most cases 
eggs were laid singly, but there was one group of 5, three groups 
of 4, and several of 3 and 2, laid by single phylloxeras. In two cases 
eggs, presumably of separate sexes, were deposited in the same group 
by the same individual, but in all other cases it appeared certain 
that the eggs laid by individual migrants were of only the one sex. 
Judging from the size, about twice as many female as male eggs 
were laid, besides quite a number (about 20 per cent) of eggs of an 
intermediate size. No male or intermediate sized eggs hatched, but 
it was noticed that the male eggs, as they developed, assumed a 
darker color than did those of the female. After, a certain point in 
the development, all the moribund eggs began noticeably to shrink 
and turn dark brown. None of the eggs showed signs of infertility, 
and within about five days of deposition hatching occurred and the 
eyes and body segmentation were visible, after which the moribund 
individuals discolored and shrank rapidly. Dead migrants were 
found occasionally on the roots and sides of the cellar jars, beside 
eggs that they had deposited. In the vineyard such a procedure was 
never observed, and therefore it is believed to be quite abnormal, and 
probably results from the inability of the migrant to escape from the 
cellar jar after having been overlooked in the periodical examinations 
for migrants. 

During the summer of 1914 a further series of experiments on the 
production of sexual eggs took place. The temperature that year 
was considerably below that obtaining in the years 1911 and 1913, 
and this may account for the lack of sexuals maturing. In 1914 the 
cages utilized in 1913 and some of other types were employed. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 89 

The experiments began June 27 and terminated September 7. Three 
hundred and ninety-seven migrants produced a total of 143 eggs 
from which no sexual forms developed. Thus the proportion of 
deposited eggs to migrants in 1913 was 1 to 3.2, while in 1914 it was 
1 to 2.75, and in 1911, 1 to 4.3. In 1914 four migrants each deposited 
four eggs, and three eggs were deposited in nine instances, but most 
of the eggs were laid singly. In no case could it be definitely said 
that eggs of more than one sex occurred in individual groups. About 
three times as many female eggs as male were deposited, and about 
one-fourth of the eggs were intermediate in size (probably males). 
The winged sexuparse died on the average two and one-half days 
after they were admitted to the cages, or about four days after they 
had transformed from the nymphal instar. 

In 1915 experiments were continued, migrants being secured from 
June 26 to October 27. Part of these were used in stender and petri 
dishes, part in small circular rubber cells ( T 3 g inch high, 1J inches 
in diameter) mounted on microscope slides with cover glasses for 
lids, and a few on a living vine (Riparia). In the dishes small 
pieces of vine, bark, or leaA^es were placed, leaves of the Champini 
being used mostly on account of the fact that the migrants prefer 
to deposit eggs on a tomentous leaf. The effect of variations in 
temperature and humidity was noted. 

A total of 1,961 migrants deposited in all 472 eggs, and 52 sexuals 
matured. Thus the proportion of eggs to migrants was approxi- 
mately 1 to 4.15. In the stender and petri dishes and on the living 
vine combined, 938 migrants deposited 167 eggs, a proportion of 5.6 
to 1, of which 16 sexuals matured. In the rubber cells mounted on 
microscope slides, 1,023 migrants deposited 305 eggs, a proportion 
of 3.3 to 1, and 36 sexed forms matured. The rubber cells therefore 
gave a greater proportion of eggs per migrant. Part of these "cells 
were kept in a cellar and part inside a slide box in a room of the 
laboratory. The egg deposition was not appreciably different in 
these two situations, but the sexes under the almost constant tem- 
peratures of the cellar matured better than under the fluctuating 
temperatures of the room. Part of the dishes also were kept in the 
cellar and part exposed to light in the room. Those in the latter 
situation averaged more eggs per migrant, but the proportion of 
sexes which subsequently matured was similar to that of the migrants 
and dissimilar to that of the eggs. 

It appeared at first that exposure to light induced the migrants to 
deposit a greater proportion of eggs and later appeared to have 
prevented a large proportion from maturing. Judging from the 
fact that the amount of light to which these eggs were subjected 
during their development was not greater than occurs under natural 
conditions, however, it would appear that this supposition is incor- 



90 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

rect and that the disproportionate mortality among the eggs was 
caused rather by the uneven temperatures prevailing in the room. 
The presence or absence of humidity had no apparent effect on the 
deposition of eggs. Eggs and sexed forms developed better in dry 
than in moist rubber cells, but in the dishes exposed to light the 
converse occurred. Part of the migrants were stimulated to fly in 
the sunshine before being placed in the cages, and deposited a some- 
what larger average number of eggs than those which had not flown, 
but the flight or nonflight of the migrants did not appear to influ- 
ence the subsequent development of the eggs and sexes. In July 
and the first half of August, when the temperatures reached a maxi- 
mum, there was a higher average in egg production and in the pro- 
portion of sexuals matured, yet during the period September 16 to 
October 27, despite lower temperatures, a larger average proportion 
of eggs per migrant and of mature sexes was produced than during 
the intermediate period from August 16 to September 15. 

On the whole, development was most successful where migrants had 
flown and when eggs were kept in moderate light and in a moderately 
humid environment. 

The longevity of the migrants, the number of eggs deposited per 
individual, and the proportion of male and female eggs laid coin- 
cided with the results of experiments in 1914. 

It is only necessary to consider the very small proportion of eggs 
laid per migrant (in 1915, for instance, 1 to 4.15) and the very 
.small proportion of eggs which succeeded in developing into mature 
sexes (in 1915, 1 in every 9) under artificial conditions to realize 
how abnormal these conditions must have been. From observa- 
tions made in California during 1915 the complement of migrant 
eggs was found to average 2.6, so that if all the migrants in the 
experiments in that year had deposited their full complement, ten 
times as many eggs as were actually deposited would have been 
obtained. European experimenters have had, for the most part, 
similar results in their study of migrants in confinement. 

In not a single instance was a migrant observed to deposit other 
than a sexual egg, so the possibility of the occurrence in California 
of a parthenoparous winged form may be regarded as excluded. 
There occurs, however, a parthenoparous nymphical form, which has 
been discussed above (p. 82). 

THE SEXUAL FORMS. 

The sexual forms (PI. VIII, j-m), male and female, issue from 
eggs deposited by the winged sexuparse or migrants. These eggs 
are of two types, male (PL VIII, /) and female (PI. VIII, //, i). 
Writers have attempted to recognize a third type intermediate in size 



THE GRAPE PHYLLOXERA IK CALIFORNIA. 91 

between the larger female and the smaller male egg, but these inter- 
mediate eggs are apparently always of the male sex. Thus there is a 
considerable variation in the dimensions of the male eggs, as, indeed, 
there is in those of the mature male insects. According to Grassi 
(11, p. 134-135) eggs producing females vary in length from 0.384 
to 0.323 mm., and in width from 0.176 to 0.164 mm. ; eggs producing 
males, in length from 0.247 to 0.250 mm., and in width from 0.152 to 
0.134 mm. He also states that eggs of the intermediate dimensions 
are fertile and are of the male sex, and that male and female eggs 
may exceed the limits in one dimension, but never in two. On the 
average the female eggs were slightly larger than the radicicole eggs 
and the male eggs slightly smaller, but intermediate eggs had meas- 
urements identical with those of the radicicoles. 

Measurements of sexual eggs, made in California in 1913, indicated 
a range in length from 0.450 to 0.257 mm., and in width from 0.171 
to 0.117 mm. A single female of these hatched (0.357 by 0.171 mm.). 
In the light of measurements made in 19i4 and 1915 it appeared that 
eggs of the sexes were similar in dimensions to those recorded by 
Grassi for Italy, except that the range in sizes was somewhat greater. 

The sexual eggs are bright shining yellow. The eggshell is very 
thin and membranous, quite differently formed from that of the 
radicicole. The egg hatches after about four or five days' incuba- 
tion, the process of hatching consisting in the sloughing off of the 
thin shell, the emerging aphid settling at the place of hatching. 
The eyes and body segmentation become visible, and the undeveloped 
appendages are carried under the body. The insect then undergoes 
four successive molts, and does not move away until it is mature. 
During the first three instars there appears but little change, except 
that the body segmentation becomes more distinct. After the third 
molt the appendages project slightly beyond the sides of the body, 
but otherwise no visible change occurs. All the molted skins are 
contained one within another, adhering to the posterior end of the 
body, and when the last molt has taken place the adult moves away, 
leaving the " nest " of telescoped skins and eggshell behind. It 
sometimes happens that the adult is unable to cast off this pad of 
skins. The mature sexuals are capable of running actively, and, 
according to European investigations, they may live for some weeks, 
thereby facilitating a meeting of the sexes. The sexuals take no 
nourishment. The female is slightly larger and the male slightly 
smaller than the newly hatched radicicole. 

DESCRIPTION. 

THE SEXUAL FEMALE. 

Orange or orange yellow ; antenna? and legs dusky grayish ; antennee longer 
than those of newly hatched radicicole. Body a little longer and wider than 



92 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



the young radicicole. Caudal segment bluntly rounded. Eyes as in the radi- 
cicole larva. When the adult issues the single egg within is small, but within 
three days it becomes very evident (PI. VIII, j) and occupies in section an area 
equal to about three-fourths of the entire insect. 



Table XXIX. — Measurements of mature sexual females of the grape phylloxera. 



Length of body 

Maximum width of body 

Length of "winter" egg'contained 

Maximum width of ''winter" egg contained 

Antennal joint 1, right, length 

Antennal jomt 1, left, length 

Antennal joint 2, right, length 

Antennal joint 2, left, length 

Antennal joint 3, right, length 

Antennal joint 3, left, length 



Mrp,. 


Mm. 


0.357 


0.464 


.200 


.215 


.313 




.172 




.017 


.0200 


.016 


.0179 


.013 


. 0205 


.013 


.0188 


.054 


. 0580 


.053 


. 0553 



THE MALE. 

Dusky orange, darker than the sexed female ; antennae, legs, and genital 
segment dusky grayish ; eyes of three facets each, red ; beak absent. Body 
quite noticeably shorter, flatter, and narrower than that of the sexed female, 
and shorter and narrower than that of the newly hatched radicicole. Genital 
organ acutely conical. 

Table XXX. — Measurements of mature males of the grape phylloxera. 



Length of body 

Maximum width of body 
Antennal joint 1, length.. 
Antennal joint 2, length. . 
Antennal joint 3, length. . 

Hind tibia, length 

Hind femur, length 



Mm. 
0.260 
.094 
.013 
.018 
.065 
.046 
.056 



Mm. 
0.334 
.154 



,071 



In confinement both sexes at first exhibit a positive phototropism, 
but after a day of maturity they seek shaded places. At first they 
are quite active, but later become sluggish. Undoubtedly they are 
much less active in confinement than in the natural state. 

Table XXXI summarizes the development of the sexed form in the 
summer and fall of 1911 and 1913. All those which reached the 
adult state were females. 

Table XXXI.— -Summarized record of sex development of the grape phylloxera, 

Walnut Creek, Calif., 1911 and 1918. 



Average incubation period 

Average postembryonic period. 
Average period of development 



Number 

of indi- 
viduals. 



12 
12 

20 



Davs. 



5 

5.83 
11.05 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



93 



In 1915, in all, there were reared to maturity 52 sexuals, of which 
9 were males, 2 of these having hatched from eggs of intermediate 
dimensions. These 2 males were noticeably larger than the other 7. 
The majority of the sexuals were reared in darkness under cellar 
conditions, the temperatures never averaging over 70.5° F. and in 
one instance falling to 61.5° F. A noticeable phenomenon was the 
death of a great number of sexes during the fourth instar, which 
appeared to be due to their inability to cast the final skin as a result 
of a deficiency of moisture. Tables XXXII and XXXIII show 
the development of the sexes in 1915. 



Table XXXII. 



-Development of sexed forms of the grape phylloxera, Walnut 
Greek, Calif., 1915. 



Individual No. 



Date of 
egg de- 
position. 



Date of 
maturing 
ofsexual. 



Develop- 
mental 
period. 



Sex. 



Average 
tempera- 
ture. 



Environment. 



1. 
2. 
3. 

4. 

5. 

6- 

7. 

8. 

9. 
10. 
11. 
12. 
13. 
14. 
15. 
16. 
17. 
18. 
19. 
20. 
21. 
22. 
23. 
24. 
25. 
26. 
27. 
28. 
29. 
30. 
31. 
32. 
33. 
34. 
35- 
36- 
37. 
38.. 
39. 
40. 
41. 
42.. 
43. 
44.. 
45.. 
46.. 
47.. 
48.. 
49.. 
50.. 
51.. 
52.. 



July 17 
...do.... 
...do.... 
...do.... 
...do.... 
July 18 
July 22 
...do.... 

...do. 

July 30 
July 31 
...do..... 
Aug. 1 
...do..... 
...do...., 
...do..... 

...do 

...do 

Aug. 3 
...do..... 
...do..... 

...do 

...do 

Aug. 4 
Aug. 5 

...do 

...do 

...do 

...do 

..do 

..do 

Aug. 6 

..do 

..do 

..do 

Aug. 25 

..do 

Sept. 1 
Sept. 22 
Sept. 24 

..do 

..do 

Sept. 26 

..do 

Oct. 6 

..do 

..do 

Oct. 7 

..do 

Oct. 13 

.-do 

..do 



July 28 
...do.... 
...do.... 
July 30 
...do.... 
July 28 
Aug. 2 
Aug. 3 
...do.... 
Aug. 8 
Aug. 10 
...do..... 
Aug. 12 
...do..... 
...do..... 
...do..... 
Aug. 13 
Aug. 14 
Aug. 12 
Aug. 13 

...do 

...do 

Aug. 14 
Aug. 15 
Aug. 16 

...do 

...do 

...do 

...do 

...do 

..do 

Aug. 17 
Aug. 18 

..do 

Aug. 19 
Sept. 8 
Sept. 9 
Sept. 15 
Oct. 4 
Oct. 9 

..do 

Oct. 10 
Oct. 12 
Oct. 13 
Oct. 21 

..do 

Oct. 22 
Oct. 24 
Oct. 25 
Nov. 1 

..do 

Nov. 3 



Days. 
11 
11 
11 
13 
13 
10 
11 
12 
12 
9 
10 
10 
11 
11 
11 
11 
12 
13 
9 
10 
10 
10 
11 
11 
11 
11 
11 
11 
11 
11 
11 
11 
12 
12 
13 
14 
15 
14 
12 
15 
15 
16 
16 
17 
15 
15 
16 
17 
18 
19 
19 
21 



9 
9 
9 

9 
9 
9 
9 
9 
9 
9 
9 
9 
9 
9 
9 
9 
9 
9 
9 
c? 
9 
9 
6 
9 
S 
9 
9 
9 
9 
9 
9 
9 
$ 
9 
9 

c? 
c? 
c? 

9 
9 
9 
9 
9 
9 
S 
9 

9 
9 
9 
9 
9 



'F. 

70. 
70. 
70. 
70 
70 



70 
70 
70 



69.8 
69.8 
69.7 
69.7 



69 

68.8 
68.8 
68.8 



68.8 
68.5 
68.5 
68.5 
68.6 
68.7 
68.7 
66.9 
64.9 
64.9 
64.9 
64.8 
64.3 
64.3 



62 

62 

61.5 

61.5 

61.7 



Cellar." 

Room of laboratory. 

Cellar. 

Room of laboratory. 

Cellar. 



Room of laboratory' 



Cellar. 



•Room of laboratory. 



Cellar. 



94 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

Table XXXIII.— Summary of Table XXXII. 

Days. 

Maximum developmental period 21 

Minimum developmental period 9 

Average developmental period : 12. 73 

Average developmental period, female 12. 65 

Average developmental period, male 13. 10 

During the developmental period preceding September the sexes 
developed in an average of 11.1 days, and in the remaining period, 
from September 1 to November 3, in 16.1 days. 

The males appeared to develop more slowly than the females, but 
a larger series might not indicate such a difference. 

The sexes, as soon as mature, were confined in a microscope-slide 
cell with a piece of vine bark and some filter paper. None lived more 
than three days, and copulation was observed in several instances, 
but on the whole the sexuals showed little activity and were not 
much attracted to each other. Several of the females partly ex- 
truded a winter egg, but chose no especial locality for oviposi- 
tion, and their action was undoubtedly abnormal. 

Mating is said to occur normally on the bark of the vine, the 
female depositing a single egg under and between the layers of 
bark. The egg is attached by a curved peduncle generally to the 
inner surface of the 2-year-old bark, but sometimes to older layers. 

The Italian investigators found that eggs were most abundant 
about midway between the base and head of the vine trunk, but that 
they might be deposited on any wood of 2 or more years of age as 
well as on buds. The egg at first is greenish yellow, and later becomes 
greenish brown, remaining so until the time for hatching in the 
spring following. The phylloxeras issuing from the winter egg are 
said always to become the gallicole (gall-inhabiting) stem mothers. 

At Walnut Creek all types of vines exposed to plrylloxera infesta- 
tion have been searched exhaustively without more than a single 
winter egg being found. Among these vines were included viniferse 
taken from phylloxerated vineyards, and viniferse and American 
experimental vines grown in pots and boxes. The single egg brought 
to light was observed in December, 1912, located under the outside 
layer of bark of a young potted vine (Champenal). This egg, after 
having been kept under observation for three weeks, died. 

From all observations in California it appears that conditions are 
unfavorable for the successful development of the sexual phylloxeras 
and, therefore, for the " winter " egg and succeeding generations of 
gallicoles. Since in some parts of France a similar condition in the 
phylloxera cycle obtains, it was concluded that some factor was 
lacking to insure successful development, and there was reason to 
believe that humidity was one of the factors until the discovery of 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 95 

the existence of the gallicoles in Arizona under dry climatic condi- 
tions appeared to disprove this theory. At present it is held that 
the phylloxera in California is undergoing, and since it was first 
introduced (about 60 years ago) has continuously undergone, a 
marked change in habits resulting from variations in the character 
of its food. Wherever the phylloxera is attacking vinifera vines its 
habits are undergoing change. In many localities the production of 
sexuals, winter eggs, and gallicoles proceeds simultaneously with 
prolific agamous radicicole infestation, and in such places speedy 
diffusion of the species obtains by reason of the winged insects and 
gallicole in addition to the wanderers. In California and in certain 
other localities the spread of the phylloxera has been slow, primarily 
because the danger from the agencies of the migrants and gall in- 
habitants has been very slight, and this notwithstanding the presence 
of resistant vines, the type on which the gallicoles normally form the 
galls and on which the " winter " eggs develop the more successfully. 
Thus it appears that the phylloxera, since it has been in California, 
has modified its habits to suit its environment, by exchanging the 
complicated life cycle on its native plants (native vines of eastern 
North America) for the more simplified life cycle upon Vitis vini- 
fera. 

THE GALLICOLE AND ITS RELATION TO CALIFORNIA CONDITIONS. 

In the eastern United States, in Arizona, and in the majority of 
the phylloxera districts in Europe the gall form or gallicole occurs. 
This is most prevalent in the more humid districts, and occurs chiefly 
on American vines and American hybrids and only rarely on Vitis 
vinifera and its hybrids. Recent research in European countries, 
especially in Italy by Grassi and his colleagues, has proved that 
the original gallicole hatches from the winter egg deposited during 
the previous autumn by the sexed female in a crevice in the bark. 
This larva hatches with the appearance of the first leaves and 
attaches itself to the surface of a young leaf, where its punctures 
produce a "pocket" formation in the leaf tissue. In this pocket it 
grows, matures, and deposits its eggs. Upon hatching, the resultant 
larvae seek young leaves higher up on the growing cane, and, settling 
on the surface, cause further pocket formations. Succeeding gen- 
erations follow throughout the summer, the numbers being more and 
more reduced by predacious enemies (Syrphidae, Agromyzidae, Coc- 
cinellidae, etc.) , and also by a certain percentage of the newly hatched 
larvae deserting the cane for the roots. Among the later genera- 
tions the percentage of larvae that seek subterranean existence in- 
creases, and such larv33 may be differentiated by certain character- 
istics, when newly hatched, from those destined to continue on the 
foliage. They possess relatively longer beaks and a different anten- 



96 BULLETIN 903, TJ. S. DEPARTMENT OF AGRICULTURE. 

nal structure, including relatively larger sensoria. To these small 
larvae has been given the name neogallicolce-radicicolce (young gall 
lice with root louse characteristics), while to the type which merely 
moves from one leaf to another younger one has been given the 
name neogallicolce-gallicolce (young gall lice with gall louse char- 
acteristics). 

On the European vine (Vitis vinifera), according to Grassi, winter 
eggs were rarely laid and galls rarely found, the majority of those 
found being imperfect. It was apparent also that growth was much 
slower than on American vine foliage. In Italy, from eggs pro- 
duced by nine gallicoles that had produced galls on a European 
vine, a few of the progeny had radicicole characteristics. This, 
however, was a rare occurrence, the great majority of young larvae 
hatching in galls on European vines showing the gallicole charac- 
teristics and thus not being destined for subterranean life. The 
Italian investigators were able to cause radicicoles to settle and 
produce generations of gallicoles on the leaves of a Clinton (Ameri- 
can) vine. This succeeded after several fruitless efforts. In this 
connection it may be said that, at Walnut Creek, on a small Golden 
Champion (American) vine, radicicoles ascending the stalk and 
ovipositing in crotches of the stem as high as 5 inches above the 
surface of the soil were observed in the fall of 1914. A few of the 
resulting larvae settled still higher up on petioles. Finally cold 
weather in November ended this aerial infestation either by killing 
the larvae or compelling them to descend below ground. 

On July 16, 1913, a shipment of eight leaves of an American vine 
well infested with gallicoles was received from Vienna, Va. The 
gallicoles were egg-laying females, probably of the second genera- 
tion (progeny of stem mothers), newly hatched larvae, and large 
numbers of eggs. Only one adult occurred in each gall. Four of 
these leaves were placed contiguous to foliage of three resistant 
vines. The varieties were Riparia X Rupestris 3309, Columbaud X 
Riparia, and Solonis X Riparia. The first two named, small vines 
in pots, each were inoculated with one infested leaf; the third vine, 
larger and growing in the Aaneyard, was inoculated with two leaves. 
In no case were galls developed on the foliage of the three vines 
inoculated. It is to be recorded that these three vines were of a 
different type from the infested vine, but the Riparia type is sus- 
ceptible to gallicole infestation. 

On September 6, 1913, a selection of foliage of a Riparia hybrid 
infested with gallicoles was received from Washington, D. C. The 
following vines growing in the vineyard were inoculated with the 
infested foliage in close contiguity: Riparia X Rupestris 3309, Ru- 
pestris St. George, Rupestris X Berlandieri 301 A, Berlandieri X 
Riparia 34 E. M., Riparia X Cordifolia X Rupestris 111-8, Riparia 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 97 

Gloire de Montpellier. The infested foliage had an abundant sup- 
ply of newly hatched larvae, but in no case did the inoculation suc- 
ceed. It is possible, however, that many of the larvae of such a late 
generation had radicicole characteristics, and therefore none such 
would settle on the leaves. Both of the foregoing series of inocula- 
tions were made under conditions of light atmospheric humidity. 
Kecent research in Italy (11, p. 335-345) (17) shows that in that 
country, at least, humidity and irrigation have much influence in the 
production of galls on resistant vines. Both the Riparia X Rupestris 
3309, and the Rupestris St. George are said by Panatelli to produce 
many galls in dry locations. It appears, however, that in general 
a greater humidity is conducive to the production of gallicoles on 
resistant vines and their hybrids. Thus out of 24 well-known resist- 
ant varieties enumerated by Panatelli, 21 produced many galls and 
3 few galls in humid localities, while in dry locations 10 produced no 
galls, 5 few galls, and 9 many galls (17). In this connection, it may 
be added that in California resistant vines have been frequently 
observed growing among badly infested viniferae and never showing 
any sign of gall infestation. On no occasion, indeed, have the writers 
ever observed phylloxera galls in California, and there is only one 
authenticated case in California of gallicoles, that being the discovery 
in August, 1884, by Dr. F. W. Morse (16), of gall-inhabiting phyl- 
loxerae on a Canada (labrusca X riparia X vinifera) vine on the 
University of California grounds at Berkeley. 

The two shipments of gallicoles cited above were also used in 
experiments to determine whether this form would live on roots. 
On July 16, 1913, 75 newly hatched gallicoles were placed on two 
pieces of severed root (Zinfandel) in a petri dish in the cellar. On 
a third smaller root 100 eggs from the galls were located. On 
August 18, on the two larger roots, five phylloxerae with the typical 
radicicole characteristics matured. On September 3 there were 
altogether seven mature egg-laying radicicoles, of which six had 
matured on the two larger roots. Thus out of 100 eggs and 75 newly 
hatched larvae only seven phylloxerae matured. 

On September 6 a similar experiment was begun on severed roots 
in the cellar. On two roots 75 eggs apiece were placed. These all 
turned black and none hatched, it appearing that the embryo suffered 
injury through fermentation that developed during the transconti- 
nental journey. This supposed fermentation did not affect the larvae 
already hatched and which were used for the foliage experiment. 

A further experiment took place on roots of a living vine (Thomp- 
son's Seedless) which was inoculated July 16 with 50 eggs. Three 
insects from this inoculation matured August 12, 13, and 14. They 
were typical radicicoles and laid eggs at the rate of between two and 
1900°— 21 7 



98 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

three daily, at first exceeding that number. These eggs were typical 
radicicole eggs, and produced further radicicole generations. Twelve 
of the eggs laid August 21-24 were transferred to another root of 
the same vine (Thompson's Seedless) and four insects matured 
between September 28 and October 5, after an average egg stage of 
about seven and one-half days and an average growing period of 35 
days. The progeny of these four became hibernants, several of which 
matured and oviposited the following spring. These experiments 
demonstrate that under California conditions it is possible for larva? 
hatching in galls to mature on the roots and become typical radici- 
coles. No observations were noted regarding the characteristics of 
the newly hatched gallicoles used in the experiments. After the 
inoculation, July 16, of 50 eggs on the root of the living vine it was 
seen that most of these eggs turned dark brown and failed to hatch. 
The observations on the hatching of this batch of eggs indicate that 
those failing to hatch were the earliest deposited, and it may be that 
the change in conditions and environment affected the embryonic 
development adversely. 

The present nonappearance in California of the gallicole and its 
work on the foliage of grapevines, a condition paralleled in certain 
portions of Europe, vitally affects the entire biology of the insect, 
since it has been ascertained that the phylloxera issuing from the 
winter egg can only exist on the leaf or petiole as a gallicole. The 
Italian investigators Grassi, Topi, Grandori, and Foa found that no 
larva? hatching from winter eggs fastened on the roots and that 
all of this generation of stem mothers (fundatrices) had the galli- 
cole characteristics. This is a very important biological point. It 
is borne out by observations in those parts of Europe where the 
gall form is absent and in which winter eggs are extremely rare. 
It is similarly borne out in the phylloxera regions of California, 
where similar conditions occur. During the winters of 1912-13 and 
1913-14, an extensive series of vines, large and small, of all types, 
many of which had been infested the previous summer with winged 
phylloxera?, and others which, while themselves uninfested, had been 
growing near such infested vines, were examined. With only one ex- 
ception, no trace of winter eggs or dead sexuals was found. This ex- 
ception consisted in the single winter egg noted under the preceding 
heading. 

EFFECTS OF WATER AND HEAT ON PHYLLOXERA. 

Experiments were carried out to determine (1) the resistance of 
hibernant larva? and eggs to water heated to various temperatures, 
(2) the resistance of hibernant larva? to submersion in water at ordi- 
nary temperatures, and (3) the resistance of eggs to the heat of the 
sun. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 99 

During the winter of 1913-14, two experiments were made on 
the resistance of hibernants to hot water. The temperatures used 
ranged from 116° to 137° F., and the duration of submergence 
ranged from one to four minutes. A temperature of 120° F. failed 
to destroy the aphids completely, while 125° F. with a submergence 
of one minute destroyed all the insects. Similar treatment of the 
roots of living vines resulted in no appreciable injury to dormant 
plants. 

The same winter, between December 3 and March IT, a series of 
nine experiments were carried out bearing upon the resistance of 
hibernant larvae to submersion in water of ordinary temperatures. 
Pieces of heavily infested grape roots were placed in petri dishes 
under about 1 inch of water. The periods of submersion ranged from 
48 hours (two days) to 1,512 hours (nine weeks). It was found that 
with the lengthening of the submersion period the percentage of 
aphids succumbing increased. A submersion of six weeks, however, 
resulted in the destruction of only 72 per cent of the aphids, one of 
five weeks in 64 per cent mortality, the final test (that of nine weeks) 
alone destroying all the aphids. In tests of from 48 to 168 hours' 
submergence the temperature of the water averaged 47° F., in the 
final test of nine weeks it averaged 55° F., and in four intermediate 
tests of from three to six weeks, 53° F. 

In the light of the results of this series of tests the fact that a 
practical vineyard submersion requires at least two months' flooding 
is not a cause for wonder. 

An observation made during the winter of 1913-14, from Decem- 
ber to February, showed that hibernant larvae can withstand short 
intermittent submersions in water interrupted by periods of low 
temperatures, even passing below 32° F. 

On June 9, 1914, two experiments were conducted, bearing on 
the resistance of eggs of the radicicole to heated water. In four of 
these tests the length of submersion was 90 seconds, and the tem- 
peratures ranged from 112.1° to 131° F. ; in the other seven, the eggs 
were submerged 60 seconds under temperatures varying from 108.5° 
to 132° F. Kesults showed that a temperature of 123° F., with an 
exposure of 60 seconds, destroyed all eggs. For practical use it is 
desirable to have a temperature of at least 125° F. 

In the experiments the eggs after treatment were placed on pieces 
of vine roots and observed for possible development. Temperatures 
of 123° F. or over killed the eggs immediately, but the lesser tem- 
peratures killed none or only a variable percentage. Those eggs 
not killed hatched normally. 

During June and July, 1914, a series of tests was made with 
radicicole eggs exposed to atmospheric temperatures varying from 
76° to 90° F. for periods varying from 5 to 60 minutes. With a 



100 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

shade temperature of 90° F., eggs exposed to sunlight were killed 
in 20 minutes. At a shade temperature of 76° F., 40 minutes' exposure 
to direct sunlight killed all aphids, but when placed in the shade 
the eggs resisted the maximum test of 60 minutes' exposure. 

It is therefore apparent that eggs can resist the sun's rays to a 
considerable extent. The extent of their resistance to atmospheric 
temperatures in the shade can not be estimated, though it is of course 
greater than their resistance to direct sunlight. The eggs utilized in 
these tests were selected at random, and therefore were in various 
stages of embryonic development. 

Experiments with the submersion in water of active newly hatched 
larvae are detailed under the heading " Diffusion," which follows. 

DIFFUSION OF PHYLLOXERA. 

In European countries four natural means of diffusion are recog- 
nized: (1) By the winged insect; (2) by newly hatched wandering 
larvae issuing from the soil; (3) by newly hatched wandering larvae 
traveling through the soil; (4) by the gall-inhabiting form. To 
these there should be added casual means, as follows: Cultivating 
instruments, vine supports and picking boxes, plants between the 
vines, man and domestic animals, water, cuttings and rooted vines, 
phylloxerated land, and old stumps. 

DIFFUSION BY FLIGHT. 

Comparing the slower diffusion of the phylloxera in California 
with that of certain European vine-growing sections, it was from the 
first doubted that the winged form was a common diffusing agency, 
in spite of the fact that its production is often abundant in California 
vineyards on the roots of vines the second and third years after the 
initial infestation. This doubt became strengthened by (1) lack of 
leaf galls in nature and failure to discover winter eggs on a large 
number of vines of different varieties known to have been infested 
by migrants, or to have been close to vines thus infested; (2) the fact 
that, in confinement, during five years, thousands of migrants were 
utilized and only 72 sexual forms were secured, and, in turn, no 
normal winter eggs. On comparing the researches of European 
observers it is found, however, that in most cases they were unable 
to raise the sexual forms in confinement in any numbers, so this 
second point is inconclusive. 

Grassi (11, p. 138-148) and his colleagues demonstrated that the 
insect which hatches from the winter egg always settles on the young 
vine leaf and becomes the gall-making stem mother (gallicole). 
They also found (11, p. 27^-280) that there occurred a nymphlike 
form which deposited parthenogenetic eggs from which issued root- 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 101 

feeding insects. This form generally occurred on resistant vines, 
but also on viniferse along with the sexuparous migrants. The indi- 
viduals exhibited much diversity in development, ranging from those 
with large wing pads to others bearing no vestige of wing pads, but 
having more fully developed eyes than the typical adult radicicoles. 
In nearly every case their eggs were parthenogenetic, the resultant 
larvae becoming root feeders. This form has been styled " inter- 
mediate," in that it is intermediate in structure between the radi- 
cicole and the winged form. Observations indicate that it occurs 
rather infrequently in California. It has been discussed under the 
heading "Nymphicals or intermediate forms" (p. 82). All the 
fully winged individuals observed in California which deposited eggs 
were sexuparous. 

To sum up, it is not believed that in California there is diffusion 
through the winged form. It is perhaps worth while to record 
some observations upon the behavior of the insects of this form in 
the vineyard. During July and August, 1914, these occurred in a 
Zinfandel vineyard badly infested with phylloxera. Previously 
roots of many of the vines on lighter soil had been dug up, and it 
had been found that a large production of migrants was developing, 
especially on vines having the external appearance of not being badly 
phylloxerated. The condition of the roots on this type indicated 
that phylloxeration had not been in progress more than two years 
and the tuberosities had not reached a stage of advanced decay ; but 
phylloxera were abundant, and it was evident that another year 
would find the vines much less thrifty. Sticky paper, tacked to 
boards, was placed in the vineyards, both on the surface of the 
ground in a horizontal position and in a vertical position. The hori- 
zontal papers were placed beside infested vines at distances varying 
from 6 inches to 5 feet from the trunks. The vertical boards were 
placed throughout the infested part and outside of the vineyard 
and extended from the soil surface to a height of 1\ feet. More 
winged migrants were obtained on horizontal boards than on the 
vertical boards in proportion to a given area of paper. The majority 
of migrants caught on the horizontal boards were found at the 
edges, indicating that they reached the papers by walking rather 
than by flight. In some cases where individuals were found in the 
middle of the sticky papers it appeared that these might have 
fallen down from canes of the vine above, but in many instances the 
phylloxera? obviously had reached the papers by flight or had been 
blown thither by the wind. Those on the vertical papers had either 
been borne by the wind or had flown voluntarily. On the vertical 
boards facing away from the prevailing wind no migrants were 
caught. Vertical boards with sticky paper were placed in the vine- 
yard on the following dates: June 20; July 7, 10, 13, 21, 24, 31; 



102 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

August 3, 7, 11, 14, IT, 20, 21, 31. Horizontal boards were placed 
July 10, 13, 21, 24, 31 ; August 7, 11, 14, 17, 21, 25, 31 ; September 
5, 11, 26. 

On the vertical boards eight migrants were captured between July 
13 and August 21, and on the horizontal boards, between July 10 and 
August 17, 51 were taken. The area of paper exposed on the vertical 
boards was 63,725 square inches, almost 50 square yards, while that 
of the horizontal boards was 7,625 square inches, not quite 6 square 
yards. The papers kept sticky for about four days on the average. 
Considering the comparatively large number of migrants captured 
on the limited areas of sticky paper, there must have been a 
heavy infestation throughout the vineyard. Winged phylloxera? were 
observed on and about the bases of vine trunks, and many were 
caught in spider webs and died. Whether the migrants deposit the 
sexual eggs in the vineyard or not, the total absence of galls on 
the vines (vinifera? and resistants) surely indicates that such eggs 
come to nought. 

From rather meager observations it appears that the sexuals require 
a high temperature, coupled with considerable humidity, for their 
successful development, and that the climatic conditions of Califor- 
nia lack the requisite combination. 

DIFFUSION BY NEWLY HATCHED RADICICOLES ISSUING FROM THE SOIL. 

In the summer of 1868, Faucon, in France, observed young radici- 
coles wandering over the surface of the soil following a heavy rain, 
which had caused the soil to crack open in drying. He also observed 
the phylloxera? to enter cracks and disappear. In 1872, he again 
observed these phenomena between August 4 and September 30. The 
year following, his observations were made from June 14 to Septem- 
ber 13, so that he was able to see wandering larva? during a period of 
three months. In 1876, Boiteau, m France, confirmed the observa- 
tions of Faucon, adding that he found that the greatest number of 
wanderers issued from vines at the periphery of the phylloxera 
" spot." Since then other observers have discussed the phenomenon 
of "wanderer" diffusion. Grassi (11, p. 351, 138, 148) and his col- 
leagues, working from 1907 to 1911, conducted a series of experiments 
with the wandering larva?. They found that these were strongly 
attracted to light and that in walking over the soil surface they did 
not go in a straight line, but deviated according to the variations of 
the surface. On a piece of glass they proceeded in a straight line and 
covered a distance of about 2 cm. the first minute. 

As regards inoculation of vines by these wandering young, suc- 
cessful experiments were carried out in Europe on vines in pots, it 
being found that the wanderers penetrated the cracks formed be- 
tween the inside periphery of the pot and the drying soil and infested 



THE GRAPE PHYLLOXERA 1ST CALIFORNIA. 103 

the rootlets growing in contact with the pot. Experiments showed 
that when sand was dry it obstructed the wanderings of the phyl- 
loxera?, but when moistened the phylloxera? might be drawn through it 
with the water. It was also found that in sandy soils water might 
occupy all the interstices between the grains of sand, repelling the 
phylloxera?, whereas in soils of other types air cavities existed suf- 
ficient to enable the phylloxera? to live. 

In California the wandering larva? were first observed in glass 
jars in which were kept phylloxerated roots in the summer of 1913. 
When such jars were removed from the darkness of the cellar to a 
light room, young larva? were observed wandering up the sides of 
the jars. In the dark cellar such wandering took place, but after 
light was admitted to the jar the wandering became much accentu- 
ated. Similar wandering of larva? was observed in the cages used 
for observations on living roots (Pis. V, VI, fig. 1; VII). 

Until 1914 no vineyard observations in this direction had been 
made, but in that year wanderers were observed in their normal 
state. For these observations, vines in a phylloxera " spot " in a 
Zinf andel vineyard 10 years old were selected. This " spot " was 
situated on light clay loam upon sloping ground, and within its 
confines wandering larva? were observed during July and August. 
These were found in greatest numbers coming from vines near the 
outer edge or periphery of the " spot." Such vines had little ex- 
ternal evidence of phylloxeration, but upon examination it de- 
veloped that the roots were heavily infested and produced many 
migrants as well as wanderers. From vines obviously moribund a 
smaller number of wanderers appeared. Wanderers also were ob- 
tained on the same horizontal boards with sticky papers on which 
migrants were caught. These were captured close to the edge of 
the sticky substance and never farther from it than 6 mm., and it 
appeared that all those taken had crawled to the papers and that 
none had been borne on the wind. On vertical papers, not even 
when placed within 2 feet of the wanderers, and to the leeward of 
them, were any phylloxera? captured. It was observed, however, 
that on favorable occasions wanderers are easily borne off by gusts 
of wind. The part of the vineyard in which wanderer activity oc- 
curred was moderately well cracked through drying. On the hori- 
zontal sticky papers wanderers were caught at points from a few 
inches from the vine trunk to 5 feet from the nearest vine and 
directly in the center of a square described with a vine at each angle. 
In this latter case either the phylloxera? had ascended by the trunk 
of the vines, and then walked 5 feet, or else they had ascended by 
means of cracks nearer the paper. In either case it is obvious that 
the spread of a given phylloxera " spot "' may result from the activi- 
ties of these wanderers without the agency of wind. 



104 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



Wanderers were first caught on sticky papers July 21 and first ob- 
served alive in the vineyard August 11. After August 18, no more 
were caught on the sticky papers, and after August 25, no more were 
observed alive. The weather during July and August was for the 
most part bright and warm. In the vineyard the wanderers were 
observed in by far the greatest abundance near the trunks of the 
vines, and it appeared that they had reached the soil surface by fol- 
lowing up the roots. No wanderers were observed on the aerial 
portions of the vines themselves. They showed much activity, wan- 
dering aimlessly around over the soil. They seemed to prefer the 
shaded parts, but appeared also on ground surface exposed to the sun. 
Large numbers were found dead close to the vine trunks, and these 
occurred in places where the soil was very fine, indicating that the 
phylloxerse were unable to progress in fine soil. Laboratory ex- 
periments bore out this supposition. Many others became caught 
in spider webs stretched over the soil surface. The character of the 
soil in the vineyard in August, 1914, was such as to enable phylloxera 
to pass from one vine to another without necessarily encountering 
very fine soil, as no cultivation had been practiced since May, 1914, 
and the vineyard had been cultivated previously only in one direction. 

As regards the capture of wandering larvae upon sticky papers, 
the data given in Table XXXIV are of interest : 



Table XXXIV. 



-Wandering larvce of the grape phylloxera; diffusion in vine- 
yard; Walnut Creek, Calif., 191J { . 



Date caught on paper. 



July 21-24 .... 

July 24-28 

July 31- Aug. 3 

Do 

Aug. 7-11 

Aug. 11-15.... 
Aug. 14-18 



Number of 

wandering 

larvae caught 



3 
1 
20 
1 
2 

1 
1 



Distance 
from nearest 
vine trunk. 



Fee'. 



Area of 

sticky paper 

on which 

phylloxera 

were caught. 



Square inches. 
135 
135 
135 
135 
135 
135 
135 



During the period from July 21 to August 18 many sheets of 
sticky paper 135 square inches in area (9 by 15) were placed on the 
surface of the ground, and wanderers were caught on 7 (see above) out 
of 32 papers. In the majority of instances the individuals were caught 
on the side of the paper toward the nearest vines, which would indi- 
cate that they arrived there straight from the trunk of the vine. On 
sides of the paper facing vines farther away it would be natural 
to expect fewer wanderers when one considers how the circum- 
ference of a circle increases in proportion to its radius, and also the 
comparatively equal diffusion of wanderers in all radii, if the vine 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 105 

trunk is considered as the central point. On two occasions wan- 
derers were caught on paper placed equidistant (5 feet) from four 
trunks of infested vines. Examinations showed that between one 
vine and another, even of apparently equal phylloxeration, a great 
variation in the production of wanderers took place. It also ap- 
peared that there was a tendency to produce these forms all at one 
time as though they had collected in a mass and then issued all to- 
gether. As regards the time of day at which they were most abund- 
ant, it appeared that more might be observed between 10 a. m. 11 and 
1 p. m. than at other daylight hours. European observers found 
that in general the wandering larvae appeared in greatest abundance 
in the early afternoon, which is the hottest part of the day. 

Vineyard observations were continued in 1915. The same vine- 
yard was used, but more attention was paid to phylloxerated vines 
on the parts in which the soil was a heavy black clay. On 
this heavy soil no wanderers appeared before July 24, and none 
was found after July 29. The larvae also were always very scarce, 
notwithstanding the fact that the soil contained numerous cracks 
which would enable the wanderers to reach the surface. On the 
lighter soil (clay loam), wandering larvae first appeared July 14, 
and they continued to issue until August 18. During this period 
of over a month about two-thirds of the phylloxerated vines exam- 
ined were producing wanderers. Between July 15 and 21 they 
were most abundant, as many as 20 or 30 living individuals being 
visible at one time beside the more heavily infested vines. In 
August hundreds of dead larvae could be seen on the surface of the 
soil around the bases of the vine trunks, and large numbers were 
caught in spider webs. As in the previous year, the vines bearing 
the largest numbers of wanderers were those of recent phylloxeration. 

In 1915, during the period of wanderer activities, the weather was 
for the most part quite hot and dry. Occasionally there were cool 
days, and on these the wanderers appeared to be as active as on the 
hot days. 

It appeared certain that the great majority of the wandering larvae 
ascended to the light by way of the main trunk of the vines, around 
which there occurred almost always a wide crack. More issued from 
Zinfandel vines than from Carignan vines equally phylloxerated, 
perhaps because the Zinfandel had thrown out more fleshy rootlets in 
May and June, and these had decayed in July while heavily infested. 
It would thus appear that many of the wandering larvae are pro- 
duced on these surface fleshy rootlets and leave them because they 
have become overcrowded or have started to decay. 

In each of the years 1914 and 1915 wandering larvae appeared in 
the vineyard over the same period, i. e., from the middle of July to 

11 All references to clock time refer to " Standard time." 



106 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

the end of the third week in August. The condition of the soil was 
about the same in both years, moisture being somewhat higher than 
usual because of extra heavy precipitation each spring. The reten- 
tion of moisture near the soil surface tends to produce many fleshy 
rootlets, and these in turn produce abundant nymphs and wandering 
larvae. Thus a wet spring results in the early production of migrants 
and wandering larvae. 

A number of laboratory observations were made on the wandering 
larvae. From these it appeared that the insects were capable of 
walking as much as 14 feet on a smooth surface, provided a strong 
light attraction was present. On fine soil their appendages became 
clogged very soon, and prevented further locomotion, but on hard 
surfaces, they progressed successfully. On warm surfaces they easily 
became " baked " to death, and in fact always lived the longest when 
least exposed to the sun, as the heating of the surface soil killed the 
aphids. Larvae easily passed over wet sand and were able to make 
headway on dry sand, but could not penetrate sand. It was found 
that the larvae could remain alive at least for three days, wandering 
around partly upon the soil and partly in cracks in the soil in a 
flowerpot subjected to an average amount of direct sunlight. 

During the summer and autumn of 1914 a number of young rooted 
vines were planted in 9-inch pots, and these were inoculated during 
May and June by burying phylloxerated roots around the stalk or by 
transferring eggs to the larger roots. These vines included viniferae, 
American nonresistants, and resistants. On the top of these pots 
and resting on the earth were fitted tightly circular pieces of wood 
with a hole in the center, through which passed the stalk of the 
vine. The whole aerial portion of the vine was inclosed in a muslin 
cage. This construction was designed to compel phylloxerae ascend- 
ing to the soil surface to make their way through the hole around 
the stalk; and having done so, they would be unable to escape by 
reason of the white muslin cage and would soon die. In October 
and November these cages were examined, and in some of them 
small numbers of dead wanderers were found, in others none, and 
in still others very large numbers. Those containing dead wan- 
derers in abundance were the ones in which the vines had been fer- 
tilized with chemical fertilizers, and there was also a corresponding 
abundance of winged migrants from such vines. The action of the 
fertilizers produced many migrants and many wanderers and in- 
vigorated the vines, yet in all cases a large root infestation by wing- 
less forms persisted through the winter following. In the cages 
above mentioned fertilizers, in liquid form, were applied periodically 
during the summer. In 1915 a similar series of vines were fertilized 
with solid fertilizers at the time of planting in early spring, and 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 107 

later observations showed that wanderers were no more abundant on 
fertilized than on check, unfertilized vines. On young vines in 
pots wanderers were often observed to ascend the vine stalks to 6 
inches above the soil surface, and in one instance on an American 
nonresistant vine (Golden Champion) several of them fastened on 
the bark and matured there (1914). This vine was never exposed 
to the brightest light and, moreover, during 1914, within a radius 
of 4 inches from its stalk was placed a glass cylinder, around the 
bottom of which was fastened 2 inches of black paper, so that the 
stem of the vine received little light. In 1915 the glass cylinder 
and black paper were removed and no wanderers settled on the aerial 
portion, although from June 29 to September 10 a limited number 
of them could be seen almost daily ascending the stalk to about 6 
inches as in the previous year. 

During 1913 and 1914 many instances were observed of wanderers 
infesting the rootlets in the pots used in the cages for observations 
on living vines (Pis. V-VII). In these cases the wanderers were 
produced on the exposed portions of the roots, and wandering off 
these, they found themselves on the surface of the soil in the pots. 
They then proceeded to pass down through the cracks around the 
inside periphery of the pot, where the soil had dried, and finally 
reached the rootlets growing against the inside of the pot. Such 
infestations occurred on rootlets from the surface to the total depth 
of 9 inches. This infestation occurred during July, August, and 
September, and in November, when the vines were pulled up, most 
of the nodosities produced by the phylloxera had rotted. In some 
cases rootlets appeared above the soil around the periphery of the 
pot, and these were infested easily and abundantly through the 
agency of wandering larvae. In the pots in which quartz had been 
substituted for earth for experiments with fertilizers, the wanderers 
were able to find their way down to the rootlets, although the cracks 
in the quartz were fewer and narrower than in the earth. It may 
be mentioned that the earth used in the pots in 1913 was a rather 
heavy dark loam, mixed with sandy loam, and in 1914 only the 
heavy dark loam was used. A layer of gravel and sand about one- 
fourth inch thick was laid on the surface, but this did not prevent 
cracking around the inside periphery of the pot. The heavier soil 
of 1914 seemed to allow of easier passage for the wanderers. 

In the spring and. summer of 1914 three vine section cages con- 
taining cuttings were placed together in a trench. Two of these were 
infested with phylloxerse throughout May and June. On July 18 
it was found that a vine in the third cage was infested with two egg- 
laying adults, each situated on a nodosity. The vines in this sec- 
tion cage never had been inoculated, and it is certain that their in- 



108 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

festation was caused by two wanderers from an adjoining cage. It 
was judged that this infestation must have occurred about June 20, 
when many eggs were hatching in the adjoining cages and many 
rootlets decaying, thus compelling the newly hatched larvae to seek 
food elsewhere. 

INOCULATIONS WITH WANDERERS. 

On July 31, 1913, 30 wandering larvae were taken from jars in 
the cellar and placed on pieces of sound severed roots in a petri dish. 
On August 13, 25 half-grown phylloxerae found roaming around in 
jars were added. All the latter deserted the roots and died, but of 
the former, three matured August 25 to September 18. A later in- 
oculation (Sept. 25) with 40 young wanderers resulted in none of 
these remaining. Another similar experiment was tried on Septem- 
ber 29, with 40 young wanderers, but it also failed. Thus out of 
135 individual wanderers only three matured. 

In 1914 this experiment was repeated, and two pieces of sound 
severed roots were inoculated in a petri dish, one with 8, the 
other with 40 wanderers. In this case a layer of moist sand was 
placed below the roots, whereas in 1913, only filter paper had been 
used. Of the smaller lot 1 and of the larger lot 20 matured. Thus 
On August 28, 15 wanderers from jars in the cellar were placed on 
the living root of a Tokay, and 3 of these hibernated and developed 
the following spring. 

In the autumn of 1913 an attempt was made to inoculate the roots 
of sound potted vines by means of wandering larvae placed upon 
the surface of the soil in the pots. For this purpose, 35 wanderers 
were placed on the soil of each of four potted vines (Resistant 
hybrid, Sept. 18 ; Agawam, Sept. 23 ; Burger, Sept. 26 ; Thompson's 
Seedless, Oct. 6). In no case did the wanderers succeed in inoculat- 
ing the roots. The soil, however, contained extremely few cracks. 

The following year this phase was pursued further. Sound pieces 
of roots were planted 4 inches below the surface in four 9-inch pots. 
On July 8, 30 wanderers were placed on the soil surface of the first 
pot, the soil being cracked from having been watered the previous 
day. The root below was never infested. The soil of the second 
pot was watered to cause it to crack extensively. After it became 
well cracked about 25 wanderers were shaken on it, July 8. An ex- 
amination of the root, August 25, showed it to be infested with a 
thriving colony of phylloxerae. In the third pot the soil was not 
watered; consequently there was no cracking. On July 12, 50 wan- 
derers were shaken out on the surface. No infestation of the root 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 109 

below occurred. The soil of the fourth pot was watered sparingly, 
and few cracks were formed. July 17, 12 wanderers were shaken onto 
the soil. No infestation of the root below occurred. Only one out 
of the four experiments resulted positively, and in that one the 
soil was very well cracked, affording access to the root. 

Inoculation of the wanderers on living vines was attempted 
through the following experiments : Five lots of four vinif era vines 
each were planted, two on light sandy loam and three on heavy clay 
loam. The vines were all young rooted vines, and they were planted 
roughly in the form of squares during the month of June. In the 
center in each one of four of the groups a phylloxerated vine (potted) 
was put in the ground at varying distances from the four surrounding 
vines. In one group the four outside vines were distanced, respec- 
tively, 14 inches, 2 feet, 3 feet, 3J feet from the central vine. In a sec- 
ond group they were distanced, respectively, 2, 3, 4, and 6 feet from the 
central vine. In the third group they were distanced, respectively, 
2, 4, 6, and 8 feet from the central vine. In the fourth group they 
were distanced, respectively, 2, 3, 4, and 6 feet from the central vine. 
In the fifth group the four vines were potted, and in place of an 
infested central vine, infested roots were buried 1, 2, 3, and 4 feet, 
respectively, from the outside vines. In this last case the vines were 
potted to prevent possibility of underground inoculation. The four 
central vines remained infested throughout the summer, but it was 
not disclosed that they, or the buried roots, produced any wandering 
larvae above the surface. The surface of the soil in the area used 
for these experiments was kept well cracked. In no instance did the 
20 outside vines become infested. 

In 1915, field experiments were conducted in a vineyard which 
had several large phylloxera " spots " both on light and heavy soils. 
The light soil might be described as a silt loam with a clay admix- 
ture, and the heavy soil was black, sticky clay. In spring a number 
of sound rooted vinifera vines 1 year old were procured and planted 
in 5-gallon kerosene cans from which one side had been cut. Differ- 
ent types of soil were used in these cans. The vines thus planted 
were kept apart until July, when they were carried out to the vine- 
yard selected and planted level with the soil at varying distances 
from vineyard vines from which wandering larvae were known to 
be issuing. To insure cracking of the soil, water was applied to 
the soil surface and also to the soil between the cans and the near-by 
vine. Wandering larvae were observed in this vineyard from the 
middle of July to August 20. In September, after the wandering 
of the larvae had ceased, the cans were dug up. Table XXXV gives 
the results of this experiment. 



110 BULLETIN 903, U. S. DEPARTMENT OE AGRICULTURE. 



Table XXXV. — Field experiments on inoculation of vines by wandering larvw 
of the grape phylloxera, Walnut Creek, Calif., 1915. 



No. of 
vine. 



Type of soil in can. 



Variety of 
vine. 







Distance 


Date of 
planting 

can in 
vineyard. 


Date of 
taking up 

can in 
vineyard. 


of vine in 

can from 

trunk of 

infested 

vine in 

vineyard. 


[July 14 
<L.do.... 

[..do 

fJuly 15 
J. .do 


Sept. 8 
Sept. 9 
Sept. 17 
Sept. 8 


Feet. 
2 
2 

1 

1J 

5 

2 

U 

1 
4 

n 
11 

u 

5 

4 

2h 

2i 

2§ 

1 

1 

n 

8 
4 
1 
3 

2. 
4 

4 
2 

n 

• ii 

5 
2 
2 
2 


iJuly 17 
l-.do.... 
...do.... 
f July 20 
..do 


Sept. 9 
Sept. 15 
Sept. 9 
Sept. 15 
.. do. . 


July 21 
..do.... 
..do.... 
■ July 22 
..do.... 
..do.... 
..do 


Sept. 9 
Sept. 17 
Sept. 15 

...do.... 
Sept. 17 
Sept. 15 

.. do... 


July 24 
..do 


...do.... 
.. do... 


...do.... 
f..do.... 
.1 .do 


...do 

Sept. 8 
.. do. .. 


I. .do.... 
/..do.... 
\July 27 
f..do.... 
..do 


Sept. 15 
...do.... 

Sept. 17 
...do.... 
...do... 


..do 


...do... 


..do 


. . do . . ^ 


..do 


...do... 


July 29 
..do 


...do.... 
...do 


..do 


...do 







Result. 



il 

12 

3 

4 

5 

6 

7 

8 

19 

10 

11 

12 

13 

114 

15 

116 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

128 

29 

30 

31 

32 

33 



Silt loam. 

do 

do 

do 

do 

do 

do 

Heavy black loam, 2 parts; silt, 1 part 

do 

do 

Heavy black clay loam 

do 

do 

Sandy silt 

do 

do 

Pure sand 

Heavy black clay loam 

Sandy silt 

Heavy black loam, 2 parts ; silt, 1 part 
Heavy black loam, 1 part ; silt, 1 part. 

Heavy black clay loam 

Sandy silt 

Heavy blackloam, 2parts; silt, 1 part 

do 

Heavy blackloam, 1 part; silt, 1 part. 

do 

Pure sand 

Sandy loam 

do 

Heavy blackloam, 1 part; silt, 1 part. 

Heavy black clay loam 

Sandy silt 



►Mission . — 

^Zinfandel. .. 
Carignan 

Zinfandel.., 

Carignan..., 
fZinfandel... 

j-Carignan 

•Zinfandel. .. 



Uninfested. 

Infested. 
Uninfested. 

Infested. 



Uninfested. 



i Entire vines died shortly after having been planted in vineyard, therefore can not be included in 
results of experiment. 

Of the 27 vines which were alive when the cans were taken up, 21 
had been planted in the phylloxera " spot " on light soil and 6 in 
phylloxera " spots " on heavy black clay. None of the latter and only 
4 of the former group became infested. Vine 6 was examined 
September 9, and an infestation consisting of 1 adult radicicole 
and about 12 larvae was found. This indicated that a single wan- 
derer had established itself on the vine. On vine 11, on the same 
date, there were found 3 adults and about 20 larvae. On vine 12 
on September IT there were 6 adults and about 200 larvse, besides 
many eggs. On vine 13 on September 15 there were over 350 phyl- 
loxerse, including some 50 adults. Vines 11, 12, and 13 were planted 
around the same infested vine. In the case of vine 13 the infestation 
was started either by a large number of wandering larvae in August 
or more likely by one or two wanderers directly after the vine was 
planted on July 21. Since in August the phylloxera generation 
cycle may be passed in less than 22 days, and since each mature 
radicicole may average 8 eggs per diem for several weeks, it would 
have been possible for the infestation on vine 13 to have developed 



THE GKAPE PHYLLOXERA IN CALIFORNIA. Ill 

from a single wanderer. Similarly, it is possible that the infesta- 
tions on vines 11 and 12 originated with one individual each. 

In all of four inoculated vines the infestations were confined to 
the larger roots, and there was no nodositous infestation such as oc- 
curred with wanderer inoculations in potted vines at the laboratory. 
This is explained by the fact that the soil in the cans did not crack 
deeply enough to reach the rootlets (none of which came near the 
soil surface) while it cracked badly around the base of the stems of 
the vines. It is therefore most probable that the wandering larvae 
passed down the vine stem. Cracks of 1 foot or more in depth were 
quite abundant in the vineyards in July and August, and it was 
possible to find rootlets such as form nodosities when punctured by 
phylloxera? at a depth of 6 inches from the soil surface. At that 
time of year there is generally in the vineyards a wide crack about 
the base of the vines, and it is through these cracks that the great 
majority of the wandering larva? ascend to the surface. In the vine- 
yard a wanderer could never be kept under observation long enough 
to be sure that it entered a crack permanently, therefore, with the 
purpose of seeking a root. Wanderers readily enter any crack which 
they can not bridge but frequently reappear after a short period 
of time. In pots they have been observed to enter whatever cracks 
they encountered, subsequently inoculating roots buried below. In 
other experiments with pots the wandering larva? have been found 
to crawl down the crack between the soil and the inner side of the 
pot and inoculate the rootlets growing around the inside of the pots. 
Also it has been observed that in the vineyard experiments the inoc- 
ulation was probably made by the wanderers crawling down the 
stem, since no other available cracks were favorable. In the vine- 
yard, therefore, it is assumed that the wanderers enter the first crack 
they encounter. 

In the experiments of 1914 with sticky papers, wandering larva? 
were captured at varying distances up to 5 feet from the nearest 
infested vine. The four inoculated vines the year following were 
2, 1J, 1£, and 5 feet, respectively, from the nearest infested vines. 
It should be said that there was a possibility that the infestations 
were inoculated by wanderers coming from infested vines at a greater 
distance. In the instance of the three inoculated vines planted in 
cans around one single vineyard vine it is reasonably certain that 
all three became inoculated from the central vine. From this vine 
large numbers of wanderers were observed to issue. 

No vines were planted more than 5^ feet away from a vineyard vine, 
the vineyard being planted 8 by 8 feet. 

The soils used in the cans were of different types, but no satisfactory 
conclusions were drawn from this feature. It was noted that the 



112 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

vines planted in lighter soils grew poorly and that the percentage 
(hat died was greater than in the case of heavy soils. 

In 1914, wanderers were taken from jars in the laboratory cellar 
and successfully colonized on pieces of roots. It was found that they 
developed into the usual type of radicicole phylloxera?. In order to 
ascertain definitely the future of wanderers observed in the vine- 
yard a thrifty section of sound grape root was transported to the 
vineyard on July 17, 1915, and 12 larvae, wandering upon the sur- 
face of the soil, were placed thereon. Four of these subsequently 
matured as wingless radicicoles between August 23 and 27, and 
before the advent of winter a considerable colony was established. 
A contemporary experiment of similar nature was carried out with 
a like result with larvae taken wandering on the surface of the soil 
in pots containing infested vines. 

In conjunction with the inoculation experiment in the vineyard 
four Zinfandel vines were planted in kerosene cans in the laboratory 
yard, and after watering to insure soil cracking they were inocu- 
lated artificially by placing the larva? on the soil surface. These 
inoculations comprised, respectively, 21, 190, 300, and 625 wanderers 
collected during the summer. Two of the cans contained sandy silt 
and two heavy black clay. In no case did infestation result. 

For another experiment two galvanizecl-iron cans, 4 by 4 inches, 
and 10 inches deep, were used. Sound pieces of vine root were placed 
in each, 7 inches below the soil surface, and the cans then filled to the 
top, one with sandy silt and the other with heavy black loam, after 
which the cans were buried, their tops at a level with the soil surface. 
The surfaces were watered to insure cracking of the soil. Between 
July 15 and August 4, several hundred wanderers were placed on the 
sandy silt, and between July 18 and August 4 several hundred on the 
black loam. On August 27 the roots in the cans were examined. 
Those buried in the sandy silt which had failed to crack much were 
uninfested, while those buried in the heavier soil bore a small infesta- 
tion, indicating that one or more wanderers had penetrated to the 
roots. 

From the results of experiments on natural and artificial inocula- 
tions of vine roots by wandering larva? through the soil two facts 
stand out: (1) Notwithstanding the large numbers of wanderers 
available or utilized, positive results were infrequent. In the years 
1913, 1914, and 1915, altogether 14 vessels containing vine roots, 
either living or cut into sections, were inoculated by placing wander- 
ers on the soil surface, and only two of these gave positive results. 
The average number of wanderers used for each vessel was about 150. 
In the vineyard experiment in 1915, only 4 of 27 exposed vines be- 
came inoculated, yet all these vines were planted near vineyard vines 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 113 

from which wanderers were issuing. It is true that the soil surface 
inside the cans was a small area — 126 square inches — and that the 
soil itself was not as thoroughly cracked as it might have been ; but 
in many instances the cans were not more than 1 foot from the 
trunks of the infested vines, therefore, from the wanderers when 
they issued, whereas in vineyards vines are set 6 or more feet apart. 
(2) The presence of cracks in the soil leading directly to roots is 
necessary to permit the wandering larvae to descend to roots, for the 
larvae can not dig their way through the soil, and during the period 
when they are issuing, rain, which might provide moisture to draw 
them into the soil or wash them onto exposed roots, is lacking. 

The writers are of the opinion that wandering larvae are the cause 
of considerable local spread of phylloxera, that is, within the vine- 
yard or district; and that they are instrumental in causing the 
formation of new phylloxera " spots " or foci. Under favorable 
conditions it has been proved that they may live for at least three 
days above the surface of the soil, and thus may be transported 
from place to place with the possibility of finally becoming located 
on a vine root. There is no reason why wanderers may not live for 
as long as two weeks on the soil surface without feeding, provided 
this surface is not heated by the sun. In one instance, after being 
placed on a piece of root, several of them wandered for as many as 
five days before settling down to feed. It may be said also that 
larvae have been found to live in water as long as nine days without 
food, and it may thus be assumed that they might remain as long in 
the open air under average conditions of temperature and humidity. 
This fact would explain how the insect may be spread from one 
locality to another by wandering larvae that lodge in such vine 
material as picking boxes (see following under " Casual agencies of 
diffusion," p. 115). 

There are certain marked instances in California vineyard dis- 
tricts where phylloxeration has developed " with the prevailing 
winds." The only wind-borne forms of the phylloxera in California 
are the winged migrants and the wandering larvae. The California 
biology indicates that the migrant has no bearing on the preserva- 
tion of the species, and therefore such phylloxeration has resulted 
from wind-borne wandering larvae. 

DIFFUSION BY NEWLY HATCHED RADICICOLES TRAVELING THROUGH THE SOIL. 

In 1914, experiments on subterranean diffusion were conducted. 
In April three Muscat rooted vines were planted in a 4-foot square box 
containing heavy loam covered with a 3-inch layer of fine sand. The 
sand was used for the purpose of preventing wandering larvae from 
emerging upon the surface and reaching the sound vines. May 20, 
1900°— 21 8 



114 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

one of the vines was artificially inoculated. The second vine was 1 
foot distant, and the third 2 feet distant from the first. On October 
10, all three vines were dug up, and it was found that the first had a 
small infestation all over the root system. The second vine had a 
small infestation chiefly on nodosities on roots nearest those of the 
first vine. So far as could be observed, the roots of the two vines did 
not approach nearer than 2 inches at the closest point, but as some of 
the terminal rootlets had died during the summer and autumn it is 
quite possible that earlier in the season rootlets of the two vines were 
contiguous. The third vine was uninfested. Its roots had been sepa- 
rated from those of the first vine by at least 12 inches and from those 
of the second vine by at least 5 inches. 

This experiment did not appear to show that subterranean infesta- 
tion was a common mode of diffusion. The condition of the roots on 
the first vine when it was pulled up showed that its summer infesta- 
tion had been large and that many wanderers had been produced; 
therefore, one would expect that some of these would have found their 
way to both of the other two vines. The earth at the time of plant- 
ing, however, had been packed very solidly, and the layer of sand pre- 
vented cracking so that there were very few, if any, subterranean 
passages affording access to the phylloxerae. 

The following experiments also were made : On May 22 two young 
viniferee (Feher Szagos) were planted in a galvanized tin, 8 by 8 by 
10 inches. Two sides of this tin were basally produced in the shape 
of a cone (PL VI, fig. 2, p. 52), and at each apex was a hole of one- 
half inch diameter. The cones were then tightly fitted into wooden 
tubes, through the centers of which ran a square passageway of one- 
half inch diameter, and the junctions cemented. The cones and 
wooden tubes were buried 8 inches below the soil surface. At the 
farther ends of the two wooden tubes similar galvanized tins were 
connected, and in each of them was planted a single sound vine 
(Feher Szagos). In this experiment the tubes were, respectively, 2 
and 10 feet in length. The conical projections were expected to draw 
the roots toward the hole, therefore toward the tubes. No earth, 
except for about 2 inches at the ends, was placed in the passage in the 
tubes. Black paper was glued on to the top of the outside of the 
wooden tubes so as to prevent entrance of light. Thus the phylloxerse, 
if they passed through the hollow inside of the tube, would not be 
influenced by any light rays. On September 23 the tins and tube were 
pulled up and the vines examined. Both central vines inoculated in 
May were well infested. Their rootlets and those of the two end vines 
had penetrated not more than 3 inches into the hollow of the tube, 
but in all four cases rootlets were abundant inside the conical projec- 
tions. The vine at the end of the 2-foot tube was well infested with 



J 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 115 

radicicoles in all stages and with a few nymphs, indicating that the 
original infestation occurred at least before August 1. The vine at 
the end of the 10-foot tube was uninfested and showed no indications 
of ever having been inoculated. 

On May 22 a similar experiment, with single vines (Carignan), 
was started, the length of the wooden tubes being 6 and 14 feet, re- 
spectively. On September 30 the vines were examined and the roots 
of the central vines were found to be well infested. Rootlets of all 
four vines had penetrated not over 3 inches into the hollow interior 
of the tubes. The vine 6 feet distant from the infested vines showed 
a good infestation, whereas the vine 14 feet away was not infested. 

Thus, wandering larvae, in two cases out of four, had found their 
way along the whole length of the interior of the tubes and had 
inoculated the roots at the farther ends of such tubes. The inocu- 
lated vines were those at the ends of the two shorter tubes (2 and 6 
feet), and the sound vines those at the ends of the two longer tubes 
(10 and 14 feet). Thus it would appear that there is a limit to the 
distance over which the phylloxerse will proceed when they have left 
a root, intent on finding new food. These experiments with wooden 
tubes demonstrated the wandering habits of the young radicicoles, 
and it may be readily understood how this subterranean movement 
may cause a phylloxera " spot " to enlarge, especially when the soil 
is cracked to any depth. 

DIFFUSION BY YOUNG GALLICOLES. 

In districts where the gall-inhabiting forms (gallicoles) are found, 
they may be the cause of diffusion. Either the branches of vines 
intertwine and the young gallicoles pass thus from one vine to 
another, or the young gallicoles are carried by the wind on to foliage 
of other vines or to the ground. Since the gall-inhabiting form is 
normally absent in California, this means of diffusion will not be 
discussed further. 

CASUAL AGENCIES OF DIFFUSION. 

CULTIVATING INSTKTJMENTS. 

During May and June badly phylloxerated vines are accustomed 
to put forth an abundance of short fleshy or fibrous rootlets close to 
the surface of the soil. Usually these are infested heavily with the 
progeny of the overwintered phylloxera. The vineyards usually are 
cultivated and hoed at this time, and these surface rootlets are fre- 
quently broken off and carried along b}^ the cultivator and hoe. 
This possible means for spreading the insect having been considered, 
a series of experiments was initiated as follows : On May 30, in the 
vineyard, pieces of infested fleshy surface rootlets were secured, 
placed in earth, and the whole transported to the laboratory. Four 



116 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

lumps of earth and roots were partially buried in the soil of a pot 
containing a young sound vine (Pierce Isabella). The earth and 
roots exposed to the sun quickly dried up and no infestation to the 
vine resulted. It may be stated that the diameters of the lumps 
varied from one-half to 2 inches. On June 4 the experiment was re- 
peated, but the infested fibrous rootlets were wrapped loosely in four 
lumps of earth with diameters 1J to 2 inches, and half buried in the 
soil of a pot having a sound vine (Cornichon) growing in it. The 
rootlets kept in good condition and the phylloxera? lived four days 
(one of which was cloudy and rainy). On September 3 it was found 
that the vine showed a rather scanty infestation. On July 16 many 
strongly infested fleshy rootlets found in the vineyard, from 4 to 8 
inches below the soil surface, were inclosed in a large piece of earth, 
half buried in the soil of a pot in which grew a sound vine (Carignan) . 
On September 3 the vine was found to be strongly infested, especially 
on its upper rootlets near the inner periphery of the pot. On July 17 
the experiment of the day previous was repeated in its entirety, with 
a Pierce Isabella vine, and on September 3 this vine was found to be 
severely infested, bearing many nodosities both on the upper and 
lower rootlets. Thus in three out of four attempts success was ob- 
tained in securing an infestation upon sound vines by placing pieces 
of infested rootlets in lumps of soil half buried in the earth of the 
pots in which those vines were growing. In practice it would very 
frequently happen that such rootlets severed by a cultural instru- 
ment would be buried several inches deep after being dragged along 
by the instrument. It is easy to understand how the insect might 
be diffused in this manner. 

VINE SUPPORTS AND PICKING BOXES. 

Vine supports or stakes (universally used), by reason of the fact 
that they enter the soil contiguous to the main stem of the vine, 
are very likely to bear phylloxera? upon them. Since the newly 
hatched larvae can live for at least three days, and probably many 
more, out of the soil and when not exposed to the sun's rays, it is 
apparent that infested stakes could be transferred to a considerable 
distance and when set out in a vineyard upon their arrival could be 
the origin of phylloxera infestation. 

Many growers have declared that in their vineyards the phyl- 
loxera? first showed evidence of their presence at a point or points 
where picking boxes coming from infested vineyards had been piled. 
If picking boxes were scattered in an infested vineyard during the 
time of the aerial wanderer migration, one can readily see that the 
opportunity would be afforded for the phylloxera? to climb upon 
them, later to be transported to other vineyards, since it is a common 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 117 

practice to use the same boxes many times in the picking season, 
and the same boxes may be used in more than one vineyard or dis- 
trict. In California, wine grapes are rarely picked before the middle 
of September, and raisin grapes are picked toward the end of August. 
In the experimental wine-grape vineyard, wandering larvae were not 
found issuing after August 25, but in young vines in pots they were 
collected well into September. The fact that the wanderers were 
not found issuing in the wine grape vineyard at the time when picking 
boxes were distributed to a certain extent invalidates the theory of 
spread by these boxes. It is within the realm of possibility, however, 
that the latest issuing wanderers remained active and alive until the 
boxes were distributed some two weeks later. Observations on wan- 
derers issuing from potted vines lead to the conclusion that the natural 
period of wanderer issuance may be considerably lengthened beyond 
that which was found to obtain in the experimental vineyard during 
the years 1914 and 1915. This longer period would include the time 
of picking wine as well as raisin grapes. 

PLANTS BETWEEN THE VINES. 

Walnut trees planted in vineyards indicate the possibility of 
diffusion through the agency of plants. The long roots of the 
walnut offer facilities for phylloxera? to spread whenever vine 
roots come in contact with them or are very close to them. That 
phylloxera? have been found moving on these roots would indicate 
that the latter often provide an underground channel of diffusion. 

MAN AND DOMESTIC ANIMALS. 

The possibility of the portage of phylloxera? by man and do- 
mestic animals should not be overlooked. The winged forms and 
aerial wanderers may be blown on clothes or animals, and thereby 
spread, or they may be picked up with wet earth. This latter chance 
is greatly lessened under California conditions, because during the 
months in which wanderers and winged migrants are produced, 
the surface soil is dry, and the winged migrant is not a factor in 
diffusion. 

WATER. 

Recognizing the possibility of the spread of phylloxera? through the 
agency of flowing water, the writers conducted the following experi- 
ments in 1914: From May 5, 11 a, m., to May 6, 11 a. m., a piece of 
severed root, infested by six adult overwintered phylloxera? and about 
100 eggs and larva?, was subjected to a stream of water for the most 
part playing directly upon the insects and flowing 6 feet to an unin- 
fested vine (Catawba) so as to effect contact with some of its roots and 



118 BULLETIN 903, U. S. DEPARTMENT OE AGRICULTURE. 

also to stand on the surface of the soil about its stem. Examination 
of the piece of severed root after the experiment was concluded 
showed that about 40 eggs and young had been washed off. Five of 
the adults suffered no injury from exposure nor did most of the 
remaining young and eggs. On July 12 the Catawba vine was found 
to bear a strong nodositous infestation. On June 6, for eight hours, 
two pieces of severed roots bearing a total of about 200 phylloxeras 
were subjected to a similar stream of water which subsequently flowed 
6 feet to a sound Mission vine. On the severed roots the majority 
of aphids were not washed off. In this instance the roots of the living 
vine were not bared, and there were no cracks on the surface of the 
soil around it. On July 27 this vine was examined and found to be 
uninfested. The third experiment took place July 29. For eight 
hours two pieces of severed roots bearing a total of about 250 phyl- 
loxeras were subjected to a stream of water which subsequently flowed 

10 feet to a sound Feher Szagos vine growing in a pot. The surface 
soil in this pot had been previously watered, and thus was cracked. 
After the experiment was concluded, it was found that very few of the 
phylloxeras had been carried off the severed roots. September 16 the 
vine was examined, but it proved to be quite uninfested. In each of 
these three experiments a fine stream of water was used and the angle 
of declivity was slight. In the first experiment only, wherein the 
roots of the living vine were actually exposed to the stream of water, 
did an inoculation through water agency occur. It is evident, how- 
ever, that diffusion may occur by means of water-borne phylloxeras. 
In the California vineyards such a condition could arise normally 
only between November and May, for in the other months it is very 
rare to have rain in any abundance. In April and May, however, 
when the phylloxeras are active, heavy rains occasionally occur, and 
sometimes on the hillside vineyards deep waterways are formed, 
exposing the roots of vines to a depth of more than a foot. 

In this connection some laboratory experiments were made upon 
the resistance of eggs and larvae to water exposure. For this pur- 
pose small-sized glass vials and distilled water at about 64° F. were 
used. In one instance, in a corked vial, 9 out of 12 eggs hatched 
from 2 to 10 days after they were placed in the water. All those 
that hatched remained on the surface, while those that failed to 
hatch went to the bottom of the vial. In another instance eight 
recently deposited eggs were placed on the surface of the water in 
an uncorked vial. Six days later all had sunk to the bottom, but 
subsequently hatched. In a third experiment 11 well-advanced eggs 
were placed on the surface of the water in an uncorked vial. After 

11 days all the eggs had hatched, six having remained on the surface 
and five having sunk to the bottom. In all three experiments the 
hatched larvas failed to fasten to pieces of roots provided for them. 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 



119 



In a fourth experiment 26 eggs were placed in water in a stender 
dish. Two days later all but four eggs had sunk, but subsequently 
all eggs hatched and none of the resultant larvae settled on the roots 
provided for them. 

Table XXXVI indicates the results of experiments bearing on the 
behavior of newly hatched larvae in water. 

Table XXXVI. — Behavior in ivater of newly hatched larvw of the grape 

phylloxera, Walnut Greek, Calif. 



Date 


Number of indi- 
viduals 
that — 


Length 
of sub- 
mersion. 


Number of indi- 
viduals after 
submersion. 




placed 
in water. 


Sank. 


Re- 
mained 
on 

surface. 


Alive. 


Dead. 


Remarks. 


May 12 

12 

27 

15 

19 

June 1 

May 24 

June 1 

16 

16 

1 

July 15 

15 


5 

4 
2 
4 
5 
4 
1 

5 

5 

6 

6 


3 
2 

2 
1 
2 
1 
4 
1 

2 
4 
2 

2 


Days. 
1 
2 
2 
3 
3 
4 
5 
6 
7 

7 
9 
4 

4 


8 
6 
2 
2 
1 
1 
1 
3 
5 


1 

8 

8 





4 
5 
5 
1 
1 
1 

7 
3 





In stender dish without cover. 
In small vial — uncorked. 

Do. 
In small vial — uncorked; sunk aphids dead. 

Do. 
In small vial — uncorked; sunk aphids alive. 

Do. 
In small vial — uncorked. 
In small vial — uncorked; sunk aphids alive, but 

none subsequently fastened on root. 
In small vial — corked. 

Do. 
In small vial — corked; one aphid subsequently 

matured Aug. 12 on severed root. 
In small vial—uncorked; one aphid subse- 
quently matured Aug. 11 on severed root. 



Note. — In all except the first experiment, distilled water was used; in the first experiment, tap 
water. 

Prior to June 16 the phylloxera? were not followed up after 
their submersion to see whether they would fasten to the pieces of 
roots provided for them because the experiments were made only 
to ascertain how many of the larvae would be alive after submersion. 
It may be noted that in some cases the larvae which sank were found 
to be alive when removed from the water and in others those that 
floated were living when removed. The phylloxerae survived as 
many as nine days on the surface of the water, and as many as 
seven days when submerged, and at the bottom of the vial. The 
experiments, however, did not continue beyond nine days, and there 
is no reason to believe that the insects could not live in the water 
many days longer than that period. The fact that they did survive 
as long as a week was sufficient evidence of the importance of their 
resistance to water. The two experiments of July 15-19 demon- 
strated that after four days in water the young larvae could settle 
on pieces of roots and later mature. In the seven- day experiment, 
none settled on the roots. In all except one of the vials distilled 
water at about 64° F. was used. The behavior of the young phyl- 
loxerae in water was characteristic. Those on the surface were active, 



120 BULLETIN" 903, U. S. DEPARTMENT OF AGRICULTURE. 



swimming around in circles, but those at the bottom remained almost 
motionless unless disturbed. 

To sum up, it appears: (1) That eggs of radicicoles hatch readily 
in water, floating and sunken; (2) that the newly hatched larvae 
may live for more than a week submerged, or on the surface film; 
(3) that these larvae are capable, at least after four days of exposure 
to water, of fixing upon roots and developing in a normal manner. 
Further proof of the ability of young phylloxerae to live submerged 
occurred in an observation made from September to November, 
1914. A Riparia cutting had been placed in a glass vial in the 
laboratory. Immediately a callus formed, and many rootlets grew 
around the inside of the vial. On September 15, 20 eggs of radici- 
coles were floated on the water surface. None of the resultant larvae 
persisting, more eggs were floated October 10. October 12 the water 
had evaporated, and four days later two young larvae had settled. 
These had hatched after the water evaporated. About 1 inch of 
water was then poured into the vial to cover completely all the root- 
lets and the two phylloxerae. October 22, three larvae were observed 
under water, one of which had been fixed since October 16. October 
27, there were visible under water, besides the original larvae of 
the 16th, six additional larvae, five of which were settled. October 
30 all seven observed on October 27 had settled and an eighth was 
visible moving over the rootlets. A small tuberosity had been set 
up by one of the phylloxerae. All the unhatched eggs had died. It 
was noted that when the insects were exposed to sunlight they moved 
their appendages actively. November 2, three settled larvae were 
visible. These included the individual on the tuberosity and the 
one which had settled October 16. All others were dead. November 
10 the only survivors were the original settler and the individual 
on the tuberosity. Shortly after November 20 all disappeared. 
Thus one individual, destined apparently to hibernate, persisted more 
than a month fixed on a root under water, and several others lived 
under water from 3 to 14 days. 

There also exists the possibility of infestation by seepage. On 
vineyards of porous soils young larvae on the surface may be drawn 
into the soil in time of a storm or irrigation. Also on steep hillside 
vineyards in the springtime, when heavy rains may fall or when a 
rise and fall in the " water table " may occur, a seepage infestation 
may take place. Any artificial irrigation during the months June 
to October invites the spread of phylloxerae because in this period 
phylloxerae occur above the surface of the soil or are active on surface 
rootlets. 

CUTTINGS AND ROOTED VINES. 

In European countries where a small percentage of the winter 
eggs are deposited under the bark of yearling wood there is a slight 



THE GEAPE PHYLLOXERA IN CALIFORNIA. 121 

danger of phylloxera infestation following the planting of a cutting 
from such wood. This danger does not exist in California, provided 
the cuttings are not " heeled in " before transportation, because the 
winter egg does not persist successfully. If the cuttings are " heeled 
in" before transportation in an infested district, the possibility of 
their becoming phylloxerated exists. Similarly, the possible danger 
from gallicoles remaining upon the foliage of canes late into au- 
tumn is nullified, because the gall-inhabiting forms do not normally 
occur in California. 

The greatest danger of phylloxeration resides in the planting out 
of infested rooted vines. This is a very abundant means of distrib- 
uting phylloxera. Even if only one or two out of a thousand vines 
are infested at planting, a " spot " or " spots " will form within a 
few years, and the whole acreage eventually will become infested. 
While the vines remain small, diffusion is slow because the roots of 
one vine are separated from those of its neighbors, and underground 
diffusion thus is rare if not impossible. Also, the relatively small 
number of roots, coupled with the relatively small number of phyl- 
loxera? able to flourish thereon, prevents many opportunities for 
aerial diffusion by wanderers. If the majority of the vines planted 
out contain phylloxera?, however, the vineyard's complete phyllox- 
eration is not long removed. In a phylloxerated district the employ- 
ment of resistant roots obviates the necessity of treating the vines 
before planting out in the vineyard, yet danger exists in cases where 
grafted vines are planted too deeply and the stouter vinifera scion 
is enabled to send out its own roots, in many instances crowding out 
the roots of the resistant stock. The scion's roots, being nonresist- 
ant, decay when phylloxerated just as though no resistant stock had 
been employed, and the expense and trouble of the grafting process 
are wasted. Even though phylloxera? live on resistant stock roots 
in grafted vineyards without necessarily injuring the crop or vines, 
there still remains the possibility that infestation will arise from 
these grafted vines and that nongrafted vineyards near by will be- 
come inoculated. Such a possibility is accentuated the greater the 
proximity of two such vine areas, and especially if the nonresistant 
area is to leeward of the grafted area or if water flows from the 
grafted to the nonresistant vineyard. It is advisable, therefore, to 
disinfect even resistant roots when these are to be planted in a region 
free from phylloxera. 

PHYLLOXERATED LAND. 

Experiments with potted vines have given proof that phylloxera? 
may live at least 10 months on buried severed pieces of roots, and 
also that such pieces may remain sound for 18 months and at the 
termination afford acceptable food for the insect. It is evident, there- 



122 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

fore, that the planting of vines on land from which phylloxerated 
vines have recently been pulled up is a dangerous procedure. It is 
next to impossible to pull up grapevines without leaving pieces of 
roots in the ground. In the case of vine nurseries, this danger is very 
apparent. 

OLD STUMPS. 

Since the phylloxeras may live under the bark of vine stumps to 
several inches above the soil surface, it is apparent that these infested 
stumps might possibly be a means of diffusion if sound vines should 
be placed near them. Such stumps, however, soon decay after they 
have been pulled from the ground and severed from their roots. In 
the active season, however, any insects dwelling upon them would 
hasten to leave and seek other food, so that in this season it is quite 
possible for diffusion to occur from the stumps. In the winter the 
phylloxeras would all be hibernants, and these would die as the stump 
decayed. 

SUMMARY. 

HISTORY. 

The grape phylloxera was introduced into California about the 
year 1858, having been brought on vines imported by settlers from 
the East. It thus appears that the pest arrived on the Pacific coast 
at least as early as it reached France, where the first evidence of its 
activity was vaguely noted in 1862. 

For many years previous to this introduction the Spanish settlers 
and Missions had cultivated on a moderate scale the Mission grape, 
and this, though a very susceptible variety, as was afterwards 
proved, had flourished without disease. About the time of the advent 
of the phylloxera grape culture was receiving a great impetus, and 
many European varieties were being introduced which shortly showed 
signs of disease in localities in which the eastern vines had been 
planted. 

The phylloxera has since spread throughout most of the grape 
districts of California wherever conditions have been suited to it, 
but never has the pest assumed such disastrous proportions as it did 
during the first years of its ravages in France. It is possible that 
the insect has never reached such isolated vine districts as those of the 
southern California counties, but in many of such isolated localities 
the conditions are unsuited to the insect, and thus we can not be 
certain that it did not reach these places and fail to establish itself. 

Coming upon the scene at the infancy of the commercial grape 
industry, the phylloxera has been present throughout the growth 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 123 

of that industry and, it is estimated, has in the course of some 60 
years destroyed about 75,000 acres of grapes. 

In many instances the insect has been distributed through the 
agency of infested rooted vines imported into an uninfested district 
or vineyard. In other cases the insect has been carried on vineyard 
material. In no instance has the distribution been as rapid as that 
which took place in the vineyard districts of France. The modi- 
fied life cycle in California, i. e., sterility of the winged form, 
coupled with topographic barriers, consisting of mountain chains and 
dividing valleys, is in very great part responsible for this. 

VINEYARD DESTRUCTION. 

There is great variation in the rapidity of the destruction of vines 
and vineyards by phylloxera. 

Apart from some variation in the different grape varieties, soil 
conditions must be considered as of great importance. In poorly 
drained soils the vines succumb much more rapidly than in well- 
drained land. Accumulation of moisture in the subsoil materially 
assists in the decomposition of infested roots, whereas if the subsoil 
is well drained, vines may flourish notwithstanding infestations ex- 
tending over many years. Vines attacked when young and before 
their root systems have become established will succumb more rapidly 
than will those infested at a greater age. 

The first indication of phylloxera in a vineyard occurs in the form 
of one or more stunted vines and a premature yellowing of the 
foliage. In time, adjacent vines will show similar indications, and 
those first infested are more noticeably stunted. Gradually more and 
more of the surrounding vines are affected, and those in the center 
become very much weakened or die outright. Thus are formed the 
so-called " oil spots " or foci for the distribution of the disease, which 
may be likened to the ever-increasing concentric circles of waves that 
are formed when a stone is cast into placid water. 

Following the initial infestation of a vine under favorable condi- 
tions for phylloxera, the insects multiply rapidly, and within two 
or three years increase their range to involve the entire root system. 
Those which settle on the growing rootlets form fleshy lesions or 
swellings, which are termed nodosities. These swellings are gener- 
ally somewhat curved, the insect inhabiting a depression of the inner 
arc. In the great majority of instances the insect stops further apical 
growth of the rootlet, and thus the rootlet ceases to supply nourish- 
ment to the vine. Although the percentage of rootlets thus infested 
is often large, a vine of vigor can easily send out more and continue 
to draw its nourishment from the soil. Other phylloxerse settle on 
the older roots and in most cases cause swellings termed tuberosities, 



124 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

which vary in size, but the majority are about one-fifth of an inch 
in diameter. They are frequently very abundant, and two or more 
may coalesce. The bark of the root often cracks longitudinally, and 
a chain of swellings arises from phylloxera punctures. As long as 
these swellings remain fresh, the health of the vine is not much im- 
paired, but as soon as they decay the vine is injured, and when they 
decay in numbers the roots are frequently destroyed, causing first the 
stunting and subsequently the death of the vine. 

BIOLOGY. 

The grape phylloxera was named in 1855 by Fitch in America 
from the gall-inhabiting form, and in 1868 by Planchon in Europe 
from the root-inhabiting type. In 1870 Riley and Lichtenstein 
proved that the two forms were two separate phases of a single 
species; consequently, Fitch's specific name vitifoliae must be con- 
ceded priority. 

In its native region, eastern North America, the insect has a very 
complicated life cycle, which includes an aerial gall-inhabiting 
form. In California the gall form has been observed only once and 
that in the year 1884. 

The California life cycle (fig. 10), as indicated by research, is 
much more simple than that which obtains in the East, and as far 
as the economy of the insect is concerned, is purely parthenogenetic. 

Winter is passed in the form of the hibernant larva. Virtually 
all hibernants are newly hatched larvae which settle down to hiber- 
nate immediately after hatching from the egg in the autumn, but 
a few hibernate in an older stage. Coincident with the first flow 
of sap in spring, these hibernants commence to feed, and mature on 
the average five and a half weeks later. The hibernant larva is light 
brown in color, and is about one-third millimeter long and half as 
wide. The mature hibernant is about 0.75 mm. long and 0.40 mm. 
wide, and does not differ from the adult radicicole of any other 
generation. On the average, it takes the hibernant six months to 
mature, the period ranging from four and a half to seven and a 
half months. The mature hibernant gives rise to a number of genera- 
tions — as many as eight — of root- feeding phylloxeras throughout the 
summer and autumn. Although somewhat arbitrary, April 15 to 
October 15 best indicates the period of the active half-year of the 
insect, the period October 15 to April 15 being the dormant or 
hibernating season. 

All forms of the phylloxera are oviparous. The average number 
of eggs per adult radicicole is about 110 and the average egg-laying 
period about 45 days. Incubation varies with temperature and lasts 
from 5 days in midsummer to over 30 days in December. The eggs 



THE GRAPE PHYLLOXERA IN CALIFORNIA. 125 

are lemon yellow and oval. Upon hatching from the egg, the bright- 
yellow larva seeks food. Larvae hatching in spring mostly settle near 
the eggshells, but in summer and autumn a considerable percentage 
travel along the roots or forsake the vine altogether, either following 
cracks in the soil to reach neighboring vines or ascending to the sur- 
face of the soil and traversing the ground in their endeavors to reach 
other vines. To those that voluntarily forsake the vine has been 
given the term " wanderers." The larvae molt four times, and on the 




Fig. 10. — Diagram to illustrate annual life history : Innermost shaded crescent, active 
period of wandering radicicole larvae ; middle shaded crescent, period of development 
of the sexuparous migrant ; shaded portion of outer circle, hibernation period of 
radicicole larvae ; unshaded portion of outer circle, period of active life on the roots. 

completion of the final molt become mature insects. At first oval, 
they tend to become pyriform as they grow. The color, yellow, 
yellowish-green, or yellowish-brown, is dependent on the nature of 
the food. The length of the developmental period varies according 
to food and meteorological conditions. On succulent living roots 
the average period of larval development was found to be about 22 
days (hibernant generation excluded), and the maximum and mini- 
mum respectively 36 and 10 days. 



126 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 

The winged form is produced from the middle of June until No- 
vember. It is more abundant in the coastal districts than in the in- 
terior valleys. In their first two instars the larvse of the winged 
form do not differ from the corresponding stages of the wingless 
form, but in the third and fourth stages they differ structurally, and 
in these stages are termed, respectively, prenymph and nymph. Both 
these forms are elongate in shape and are light greenish-yellow or 
yellowish-brown. The nymphs have two pairs of grayish-black wing 
pads. The winged insect is orange in color with grayish-black head 
and thorax and two pairs of scantily veined wings. 

The nymphs transform in most instances near the surface of the 
soil and the winged migrants issue on the surface and fly about in 
the vineyard and neighboring regions. 

The winged insects deposit eggs of two kinds, viz, male and 
female, and the insects which mature from these eggs are the true 
sexes. These forms are unable to take food, and under normal con- 
ditions mate upon reaching maturity and the female forthwith de- 
posits a single egg under the bark of the vine. This egg hatches in 
spring and gives rise to a series of generations of gall-inhabiting and 
gall-making wingless aphids. A certain percentage of larvae born in 
the galls, however, migrate to the roots before taking food, and in 
this way the species returns to the soil. 

In California, under natural conditions, it is doubtful whether 
any sexes mature and still more doubtful whether any winter eggs 
hatch. Laboratory experiments indicate that the sexes mature in 
about 12 days. 

In the late autumn, along with the nymphs are found curious 
forms intermediate in appearance between adult radicicoles and 
nymphs. These are called intermediates or nymphicals. They are 
not abundant and all those whose progeny have been observed were 
parthenogenetic. 

The diffusion of the phylloxera is effected in nature by the wan- 
dering newly hatched larvae of the radicicoles during summer and 
autumn. These pass from vine to vine, either on the surface of the 
soil or through subterranean cracks or pathways. They may also be 
borne by the wind or on vineyard material, such as picking boxes. 
Probably water is responsible for some diffusion in hilly or irrigated 
vineyards, and cultivating instruments by picking up pieces of in- 
fested roots may effect fresh infestations. The phylloxera is easily 
introduced into a vineyard or section by the practice of planting 
infested rooted vines to make up for cuttings which did not succeed 
in previous years. 



LITERATURE CITED. 

(1) Bancroft, H. H. 

1883-1888. History of Mexico. 6 vols. maps. San Francisco. 

(2) Bioletti, P. T. 

1896. Investigations of various types of grapes, their adaptability to 

different localities, and their value for wine making and other 

purposes : Made during the seasons of 1887-1894. In California 

Expt. Sta. Report of Viticultural Work . . . 1887-93, p. [17]- 

372. (See p. 288.) 

(3) Bioletti, F. T., and Twight, E. H. 

1901. Report on conditions of vineyards in portions of Santa Clara Val- 
ley, California. California Univ. Agr. Expt. Sta. Bui. 134, Sept. 
23. 11 p. 

(4) California, Board of State Viticultural Commissioners. 

1881. First annual report. Ed. 2, rev. Sacramento. 

Pages 29-30 : Report of Mr. G. G. Blanchard, Commissioner for the El Dorado 
District. 

Pages 108—111 : Appendix C : The Phylloxera-vastatrix and its ravages in 
Sonoma Valley. By H. Appleton. 

Pa~e 112 : Appendix D : History of the Orleans Hills vineyard and its diseases. 
By J. Knauth. 

(5) California, Board of State Viticultural Commissioners. 

1888. Annual report . . . for 1887. Sacramento. (See p. 47-48.) 

(6) California Farmer. 

1855. Catawba grape. January 23, 1855. 

(7) California State Agricultural Society. 

1859. Transactions for the year 1858. Sacramento. (See p. 312.) 

(8) California University College of Agriculture. 

1883. Report of the professor in charge to the president, being a part 
of the report of the regents of the University, 1882. Sacra- 
mento. (See p. 172.) 

(9) Fitch, Asa. 

1856. First report on the noxious, beneficial and other insects of the 

State of New York . . . Albany. ( See p. 158. ) 

(10) FONSCOLOMBE, BOYER DE. 

1834. Sur les genres d'hymenopteres Lithurgus et Phylloxera. In Soc. 
Ent. France, Annales, v. 3, p. 219-224. 

(11) Grassi, Bat^tsta, et al. 

1912. Contributo alia conoscenza delle Fillosserine ed in particolare 

della Fillossera dell a vite . . . seguito da un riassunto teorico- 

pratico della Biologia della Fillossera della vite (con una 

tavola ) della Dott. Anna Foa. Roma, 1912. E-L, 456, lxxv p. 

illus., pi. 

Bibliographia, p. 419-431. (See p. 12; 134-135; 335-345; 351; 
138-148; 274-280.) 

(12) GUERCIO, GlACOMO DEL. 

1900. Prospetto dell'Afidofauna Italica. In Nuove Relazione R. Staz. 

Ent. Agr. di Firenze, ser. 1, no. 2, p. [l]-236. 

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